Churchill's Bomb

by Graham Farmelo

  The Society did not film the Prime Minister signing its Charter Book, so we shall probably never have the pleasure of seeing the looks on the faces of the witnesses A. V. Hill and Henry Tizard. Hill was still fronting a campaign against what he saw as the government’s inept use of its scientists;34 Tizard had submitted his report on the mission to the US several months before but had not heard a word from Churchill since.35

  The Prime Minister kept the Fellows waiting for forty minutes. Meanwhile, his Private Secretary Jock Colville chatted with them, probably touching on the news that the King’s Birthday Honours List had elevated Lindemann to a peerage. The Prof took the opportunity to shed his surname, with its hint of German and Jewish origins, and took the name Lord Cherwell (pronounced char-well), after the river that meanders past Christ Church Meadow in Oxford. As Colville knew, this was an unpopular appointment. In private, many scientists defied polite convention and continued to refer to the Prof as ‘Lindemann’ (the name that will continue to be used here).36 Tizard, who at the same time turned down Churchill’s comparatively paltry offer of a junior appointment in the Order of the British Empire, could not resist commenting that ‘the Cherwell is a small and rather muddy stream’.37

  Ten days later, on the morning of 22 June, Churchill was awoken at Chequers with news he had been expecting for some weeks: Hitler had double-crossed Stalin by unleashing 148 divisions of the German army – some 3.2 million men – against the Soviet Union. In the first weeks of this vast eastern conflict, the Nazis appeared to be capable of storming all the way to Moscow.

  In a radio broadcast that night Churchill announced that although he had spent twenty-five years opposing Communism, any state that fought Hitler would have Britain’s aid, so ‘We shall give whatever help we can to Russia and the Russian people.’ Most of the top brass in the British military expected the Wehrmacht to crush Stalin’s army within months, but the good news was that Britain and its Empire were no longer fighting alone. Though Hitler seemed to be turning his attention away from Britain, Churchill was taking no chances: he put British defences ‘on concert pitch for invasion from September 1st’.38

  Reports of the mood in Washington were encouraging for Churchill, who heard from the new British Ambassador in Washington, the former appeaser Lord Halifax, that Roosevelt privately no longer doubted that the US would have to enter the war.39 During another visit to London in July, Harry Hopkins – arriving laden with supplies of ham, cheese and cigars – was even more upbeat, and soon afterwards Churchill received the news he had longed to hear: the President had consented to meet him.40 It was agreed that they would convene in Placentia Bay, Newfoundland, so the Prime Minister would have to cross the U-boat-infested Atlantic.

  On 1 August, the Prime Minister set off, unable to contain his excitement.41 Brushing aside Roosevelt’s suggestion that only the two of them needed to be involved, Churchill took along a retinue that would have been the envy of a medieval monarch – dozens of officials, servants, journalists, several ministers and, of course, Lindemann, who was about to have his first experience of international diplomacy at the highest level. Over the past few weeks, the Prof had been keeping a close eye on the MAUD committee, whose final report was about to begin its journey to Churchill’s desk.

  It had been almost seventeen years since Churchill had first alluded to the possibility of nuclear bombs in ‘Shall We All Commit Suicide?’ At that time, in 1925, he had struggled to maintain his usual optimism as he urged the leaders of the human race, able for the first time to exterminate itself, ‘to pause and ponder upon their new responsibilities’.42 Now, he was about to become the first head of government to decide whether to go ahead with building the most destructive explosives the world had ever seen. The report on which he would be obliged to base his judgement was being written mainly by James Chadwick, who had helped to realise the vision Churchill set out in ‘Fifty Years Hence’ by discovering ‘the match to set the nuclear bonfire alight’.

  JULY AND AUGUST 1941

  Chadwick believes Britain should build its own Bomb

  ‘. . . we entered this project with more scepticism than belief . . . As we proceeded we became more and more convinced that . . . conditions can be chosen which would make it a very powerful weapon of war.’

  MAUD REPORT, finalised by James Chadwick, July 1941

  A few years before his death in 1974, Chadwick told an interviewer that the spring of 1941 was still clear in his mind: ‘I realised then that a nuclear bomb was not only possible – it was inevitable.’1 He knew, too, that scientists everywhere would sooner or later find this out, that nuclear bombs would be built and that ‘some country would put them into action’. In the interview, Chadwick said that the strain of having to keep this a secret led him to start taking sleeping pills. He added: ‘I’ve never stopped.’

  Like almost all the other MAUD scientists, Chadwick was living in a city under attack by the Luftwaffe. In early May, the German bombers had targeted Liverpool seven nights in a row, killing almost three thousand people and doing terrible damage, especially to the docks. Although the worst of the attacks seemed to be (and were) over, the Chadwick daughters were evacuated to Canada a few weeks later, leaving their parents to rattle around their blacked-out home, waiting every night for more bombs and parachute mines to fall. As soon as the air-raid sirens went off, the Chadwicks went down into their cellar, damp but well stocked, a private refuge from the bombs. Chadwick’s house was never hit, but his department was less fortunate – its windows were blown out so often that he had them fitted with cardboard shutters.2 He knew, however, that the harm done by the hundreds of explosives that had been dropped on the city was trifling compared with the carnage that would follow the use of a single nuclear weapon.

  Most of the MAUD scientists agreed with Chadwick that nuclear weapons were destined to be more than speculation. Peierls had emerged as the project’s leading mathematical physicist, coordinating and checking the results of his fellow theoreticians and working closely with experimenters. Grappling with dozens of thorny calculations, he was forced to cast around for help. High-quality British theoreticians were in short supply, but he found an excellent candidate among the few foreign-born scientists who had not moved on to America – the young applied mathematician Klaus Fuchs, a refugee from Nazi Germany, now making a name for himself at the University of Edinburgh.3 MI5 began to worry when its investigators unearthed evidence that Fuchs had been an active Communist when a student in Germany, though there was no evidence that this sallow, taciturn man was any longer a security risk. Fuchs would be useful to the project only if he knew what it was planning to achieve, so – as Peierls pointed out to the dithering authorities in MI5 – he should either be rejected or cleared. Within a few days they agreed to give Fuchs security clearance, and by the end of May he was working at his desk in the Nuffield Building, and living with the Peierlses, who quickly made him one of the family.4

  Although persuasive, Peierls’s calculations and data from dozens of fission experiments could not prove that a uranium bomb would work. Without actually building one, no one could be certain that sufficient neutrons would be emitted quickly enough from a fissioning uranium nucleus, and in the necessary energy range, for there to be an explosion. Uranium atoms containing 235U nuclei were so rare that no researcher had produced enough of them to be weighed by even the most sensitive equipment.

  Lindemann’s Oxford colleague Francis Simon believed it was best to isolate 235U using the technique of gaseous diffusion, which involved forcing uranium hexafluoride gas through fine membranes, separating 235U from the slightly heavier 238U. To produce enough fissile uranium to make a weapon would require a large and complex industrial plant, which – according to Simon’s early calculations – would occupy about forty acres and set the Treasury back some five million pounds. This cost was roughly a tenth of the UK’s weekly expenditure on the entire war effort, so it would be a huge financial challenge to embark on the project, though not out
of the question.5

  To arrive at these estimates, Simon worked closely with Metropolitan-Vickers, Britain’s largest firm of electrical engineers, and with ICI, which had set up a secret war committee to coordinate the company’s work for the government.6 Lord Melchett, a strong presence on that committee and a regular at MAUD meetings, had been in close touch with Lindemann since the war began. The two of them often talked over dinner at the Savoy about everything from Britain’s agricultural policy to the latest gizmos from ‘Churchill’s Toyshop’.7 G. P. Thomson made Melchett and his fellow industrialists feel as much at home on the committee as the professional nuclear physicists – no mean feat, as some of the physicists were ill at ease working with industrial leaders. ‘This country has been sadly let down by its industrialists – who were, and in some ways still are, its government,’ Oliphant groused.8

  During the committee’s discussions, Melchett and his friends at ICI saw a juicy business opportunity – if they funded Halban and Kowarski’s experiments, the investment was likely to yield good returns after the war, when nuclear power would probably become commercially viable. Melchett soon offered to take over that part of the MAUD project lock, stock and barrel. Later, he went further and agreed to maintain the investment even if it proved necessary to continue the programme in North America – in the long run this was likely to be money well spent.9 The question of whether to work closely with the Americans on nuclear weapons research was becoming more controversial by the week. Oliphant and Cockcroft could not wait to begin a collaboration, and Thomson was encouraging, once commenting with toe-curling condescension that it would both save time ‘and give the Americans and Canadians experience’.10 Chadwick was, as usual, cautious: ‘The time has not yet arrived to take a decision on the question of moving to America,’ he had commented at a MAUD meeting in April.11

  Several of the MAUD scientists attended some of the dinners and receptions in honour of James Conant, whose eight-week courtship by his British hosts sometimes lapsed into an unseemly obeisance. In late March, he accepted an invitation to the Blacketts’ apartment in Westminster, where the two men talked over dinner with Cockcroft and Philip Joubert de la Ferté, a senior commander in the Royal Air Force.12 The Englishmen asked Conant about his meetings with their Prime Minister, but it is unlikely that they will all have shared their disappointment over what they believed to be the government’s misuse of academic scientists in the war.

  The only British scientist to sound out Conant about the possibility of building nuclear weapons was Lindemann. He surprised Conant by taking him out to dinner at a gentlemen’s club and talking openly about nuclear chain reactions, a subject the American believed to be too highly classified to discuss, even in private. When Conant took the familiar line that such work might prove useful but only in the distant future, Lindemann abandoned secrecy and briefed him on Frisch and Peierls’s work. This was the first time Conant had ever heard it seriously suggested by a scientist that nuclear weapons might actually be built, though he returned home knowing nothing of the MAUD committee’s conclusions.13

  In the late spring of 1941, Thomson started writing his report and arranged for the committee to discuss it on 2 July. Chadwick worried that their findings were being brought together in too much of a hurry, and the first draft confirmed his fears. A few days before the meeting he sent the committee secretary a powerfully worded letter listing seven criticisms of its content and hinting that he regarded it as inadequate, though he was too much of a gentleman to say so explicitly.14 The meeting, held in the Royal Society’s headquarters, would turn out to be the MAUD committee’s last. Apart from Blackett, all the leading members were there: the British scientists and their foreign-born colleagues, who were no longer regarded as serious security risks. Lindemann sat alongside his Oxford colleague James Tuck and Lord Melchett, who brought along two ICI scientists. Also present was the American physicist Charles Lauritsen, representing America’s National Defense Research Committee office in London, set up by Conant during his recent visit.15

  The MAUD committee agreed that its chairman’s draft needed polishing and that Chadwick was the best person for the job. By some distance the best nuclear physicist among them, he was also a writer of muscular but precise prose and could be relied on to summarise their consensus. Even better, he got on well with the Prime Minister’s éminence grise and respected him. Lindemann returned the compliment, admiring Chadwick’s quick brain, his straightforward manner and, in all probability, his Conservative politics. Speaking near the end of the meeting, the Prof proposed that the final report should stick to physics, keep away from politics and economics, and focus on the viability of nuclear weapons rather than on the less pressing matter of nuclear power – advice Chadwick was content to follow.

  With his customary health-threatening zeal, Chadwick applied himself to the task of collating all the research and turning it into a readable, authoritative document. Occasionally assisted by his colleague Jo Rotblat and by Otto Frisch in Birmingham, Chadwick wrote the report mainly in his office in the physics department at Liverpool University, often consulting his fellow scientists in university laboratories, ICI and Metro-Vickers. It was not easy for him to work at home – like every other building in the city, his house was blacked out after sundown, forcing him to read or write by candlelight. Sometimes, he would take a few hours off and listen to recordings of his favourite music – including Verdi operas and Mahler lieder – on the gramophone he had built at home in his workshop.

  Following the guidance of the committee, Chadwick decided to prepare two reports – ‘On the Use of Uranium for a Bomb’ and the much shorter ‘On the Use of Uranium as a Source of Power’.16 Each would begin with a section briefing lay readers on the substance of the case he and his colleagues wanted to make, followed by technical appendices that spelled out the costs and other details. In mid-July, he was struggling to meet the deadline and was working on the manuscript twenty hours a day.17 When he finally finished what became known as ‘the MAUD report’ (invariably in the singular), he was exhausted and felt ‘very down’ – all he wanted was a quiet weekend and then a restorative family vacation, involving nothing more onerous than ‘a little gentle fishing’.18

  The report concluded that a uranium bomb was possible and ‘likely to lead to decisive results in the war’, and it urged the government to pursue the project as a matter of ‘the highest priority’, building on the nascent collaboration with American scientists.19 The effort of building the Bomb was not likely to be wasted, it argued, because no nation ‘would care to risk being caught without a weapon of such decisive capabilities’, except in the unlikely eventuality of worldwide disarmament. Chadwick wrote that the Bomb could be built in only two and a half years, a figure he attributed to the advice of Metropolitan-Vickers and ICI, which spoke with more authority than anyone else round the table about industrial planning.

  On 29 July, the report began its meandering way towards the government’s Scientific Advisory Committee, which had the job of reviewing it. Chadwick had put together a document that had the clarity and directness of the Frisch–Peierls memorandum, but was even more readable. It was quite an achievement to forge such a powerful case from the opinions of so many contributors. Even Chadwick, however, could not resolve the most vexed disagreements among his MAUD colleagues, and he had no alternative but to dodge the crucial question of whether Britain should attempt to build the weapon on its own soil. Predictably, debates about this unanswered question were raging in Whitehall.

  Tizard said that it would be ‘absurd’ to try to make nuclear bombs in the UK during wartime and argued that Britain should collaborate with the United States.20 Blackett agreed. In a dissenting note to the Air Ministry, he wrote that it was unlikely that such a weapon would be ‘of use in this war’ and that the authors of the report were wrong to believe that the first bomb could be ready by the end of 1943. His colleagues had not allowed enough time for the delays that were certain to slow down s
uch a large and novel project, Blackett believed.21 The full-scale plant should not be constructed in Britain, he recommended – a final decision on whether to build it in North America should be taken only after British scientists had visited colleagues in the US to discuss the project’s viability.

  During the week Blackett’s letter was circulating among officials, a cat was thrown among the pigeons by Charles Darwin, a grandson of the great naturalist and a theoretical physicist then serving as Director of the British Central Scientific Office in Washington DC. In a handwritten note to Hankey, each of its five pages marked SECRET, he pointed out that it was high time for Britain and America to decide whether they were serious about developing nuclear bombs or, perhaps, conclude that these weapons were too destructive to contemplate.22 He had been talking with Bush and Conant, who floated the idea that the two countries should go beyond coordinating their research on the Bomb and regard it as ‘a joint project of the two governments’. Darwin recommended that Britain send a delegation of physicists – including Chadwick, Thomson and Simon – to try to agree on a joint policy with their American colleagues.

  Hankey refused to be hurried by Darwin or anyone else.23 He began to plan a careful review process, aiming to cross-examine all the scientists involved in order to probe every detail of the MAUD report and check the validity of its recommendations. The Hankey committee would have to do without the advice of Thomson, who had dropped everything and hurried to New York in mid-August, after hearing that his wife had been taken gravely ill. Before leaving, he asked Chadwick to take over the running of the project, commenting that it looked likely that a nuclear-bomb factory would be set up in Britain, a prospect Thomson regarded as so impracticable that it was ‘deplorable’.24 The handover to Chadwick would turn out to be important, as he was one of the few MAUD scientists who agreed with Lindemann and Melchett that the Bomb should be built on home soil. Now that he was no longer out of the picture, it was much more likely that Lindemann and Chadwick’s view would prevail.