Thus on Saturday 10 May 1941 Peierls sent his letter to Fuchs setting out the terms and inviting him to join in work ‘for the Ministry of Aircraft Production’. Peierls added that he ‘cannot now disclose the nature or the purpose’ other than to say that it involved ‘mathematical problems of considerable difficulty’. The job would be ‘temporary, probably for six months at a time’, though ‘I do not see an end to the work at present’. Peierls’ letter of 10 May was probably the formality required to complete rather than initiate the move. Fuchs would have received Peierls’ letter on Monday 12 May at the earliest; by 13 May the Edinburgh City Police had already given him permission to travel by night train to Birmingham so that he could talk the offer over with Peierls. Whatever the truth, Peierls, Born and Fuchs certainly moved faster than the Security Services.
Fuchs carried with him a handwritten letter of introduction from Born to Peierls. The letter refers to ‘war work’, which is ‘important as you yourself say’. This strongly suggests that Born and Peierls had had some unrecorded conversation because there is no mention of the ‘importance’ of ‘war work’ in the available written correspondence, which had focused on Fuchs as a teacher and part-time assistant to Peierls. The correspondence between 10 and 16 May also suggests that Born and Peierls were tying up loose ends such as in a cunning scheme to get round some bureaucratic restrictions. The money for Peierls’ war work came from the Ministry of Aircraft Production. This would be a serious problem in the case of Fuchs, who was still classed as an enemy alien. Peierls suggested a clever solution: if Fuchs were to remain technically in the employment of Edinburgh University, he could then be ‘lent’ to the Ministry, who would ‘refund the salary’ to the university. Peierls added that this ruse ‘might facilitate [Fuchs’] return to Edinburgh when the temporary job expires’.
Born agreed that Fuchs’ later career would be helped ‘if he had a war job and a good record’, but then raised a problem with Peierls’ suggestion: Fuchs, unfortunately, was not in the employ of the university. Born immediately proposed a way around this too, however: he would declare Fuchs to be his ‘personal assistant’ and receive the money for Fuchs. He also looked forward to getting Fuchs back to Edinburgh ‘when the work with you is finished’.
With no clear evidence against him, Fuchs’ scientific transfer moved on rapidly. On 27 May he relocated to Birmingham, and lodged in the home of Rudolf and Genia Peierls and their two children, aged five and seven. For the first time in many years, and perhaps in his entire life, Fuchs experienced the genuine happiness of being part of a close-knit, loving family. He found the Peierls’ children amusing, and in turn they liked him. Genia’s personality provided motherly care as Klaus Fuchs was treated ‘like a son’. She found him to be ‘exceptionally companionable and nice with children, very kind, and extremely reliable’, and recalled that Klaus liked animals: ‘He was good with dogs and cats. Dogs liked him!’ She theorized this was due to his shyness: ‘He never pushed with his personality. Some people like [a] more outgoing personality but children and animals like reserve.’
In Rudolf Peierls’ home, he and Fuchs discussed physics, but the secret project was off limits. This was the beginning of a deep friendship that developed over the next decade. Of course they shared Germanic roots, but also a common style of behaviour, even down to small details at mealtimes. The Peierls’ home was like a hostel for transient scientists – ‘every British physicist of note has spent an evening at our home’, Genia would later claim. In this warm-hearted environment Klaus Fuchs absorbed the Peierls’ sense of honour, and became part of a ‘physics family’ that shared its members’ lives beyond just equations. All this would come out later. Conversation often focused on their common heritage. That Fuchs openly espoused anti-fascist and socialist views was of no particular surprise to Rudolf and Genia Peierls. His views about the Nazis mirrored theirs; that he had adopted such a stance, when as an Aryan he could have taken the safe option and stayed silent, only added to his attraction. So by the end of May 1941, Rudolf Peierls seemed to have achieved an ideal situation. He had found a talented assistant for his physics research, a fellow refugee from Nazi Germany who shared many of his ideals, and who had become a welcome and congenial addition to his family home. What could go wrong?