They went back to the War Office and continued. Fuchs agreed with Perrin’s suggestion that the most important information he gave the Russians came from Los Alamos. When he was talking about his meetings with Raymond in Santa Fe, he said at one point: ‘They asked me what I knew about the tritium bomb, the super. I was very surprised because I hadn’t told them anything about it.’
Perrin said: ‘Let me get this clear. They asked you what you knew?’
Fuchs: ‘Yes… I hadn’t told them anything about it. I was surprised.’
‘Did you tell them anything?’
‘I gave them some simple information. I couldn’t explain it to Raymond because he wouldn’t understand a thing. All I could give them was something on paper.’
They finished at four o’clock and, so far as Fuchs was concerned, that was that. He went back to Harwell and left Perrin to stay and write up his notes, as a third-person summary of what Fuchs had said. It began: ‘First period. From 1942 to December 1943. Fuchs told me that his first contact was in early 1942. By this time, he had joined Professor Peierls’s team at Birmingham University…’
Later, Fuchs would add more details, but this made it clear to anyone with even a nodding acquaintance with the atomic bomb project that what he had done was of enormous importance. For instance, concerning his second report to Raymond in Santa Fe: ‘This second report fully described the plutonium bomb which had, by this time, been designed and was to be tested at “Trinity”. He provided a sketch of the bomb and its components and gave all the important dimensions. He reported that the bomb would have a solid plutonium core, and described the initiator, which, he said, would contain about fifty curies of plutonium…’
At the end of his summary of what Fuchs had said, Perrin added a paragraph: ‘I formed the impression that throughout the interview, Fuchs was genuinely trying to remember and report all the information that he had given to the Russian agents with whom he had been in contact, and that he was not withholding anything. He seemed, on the contrary, to be trying his best to help me to evaluate the present position of atomic energy work in Russia in the light of the information that he had, and had not, passed on to them.’
By now Attlee, and the Attorney-General, Sir Hartley Shawcross, had been informed of Fuchs’s confession. Shawcross asked for a full account of what Fuchs had done, so Perrin sent him his report. It reached him in Liverpool, where he was on the political campaign trail, for a General Election was now in progress. Perrin did not keep a copy.
Meanwhile, world events thrust nuclear weapons, which had never been far from the thoughts and fears of the world’s public since the Cold War began, into the forefront again. After the revelation the previous September that Russia possessed the atomic bomb, a small number of people in America, with Edward Teller prominent among them, began to press in secret for a programme to move on to a yet higher level of destructiveness, and try to develop for the United States a hydrogen bomb. This was the ‘super’ that had been discussed at Los Alamos during Fuchs’s last months there. The concept was still unknown to most people. A secret debate took place over three months among a small number of people who did know of the possibility — it was no more than that; the pro-super group won. On 31 January President Truman announced that he had directed the Atomic Energy Commission to work towards the development of a hydrogen bomb.
Otto Frisch, who had started the British bomb project along with Peierls and had followed it through at Los Alamos, was now a Professor of Physics at Cambridge University and no longer had anything to do with weapons. He had given a number of radio talks on the BBC explaining atomic physics for the layman. After Truman’s announcement, the BBC telephoned Frisch and asked him whether he could give a talk explaining the principles of the hydrogen bomb, to be broadcast later that week. Frisch agreed. Then it occurred to him that he ought to have someone check the script in case he unwittingly committed a breach of security. He telephoned Fuchs at Harwell and asked him whether he would go over the script for security purposes. Fuchs apologized and said he was very busy at the moment. He suggested that he ask Perrin. So Frisch telephoned Perrin, who agreed to do so.
Shawcross decided that Fuchs should be arrested. He interrupted his election campaigning and returned to London to consult Scotland Yard. The American Government was told as well, because American secrets had also been given away.
The man chosen to arrest Fuchs was the head of Scotland Yard’s Special Branch, the section dealing with subversive activities, Commander Leonard Burt. He conferred with Perrin. They decided that it would be disturbing for Harwell staff if he were arrested there. Burt said, ‘Would you be prepared to ask him to come to your office in Shell-Mex House and not tell him why? Then I can charge him there.’
Perrin said he would, but he did not want to be present when Fuchs was arrested. After all, they had been colleagues and, so far as Fuchs was concerned, they were still colleagues. They decided on a plan. Perrin’s office had two doors; one led to the anteroom, where his secretary sat, and the other led out into the corridor. Perrin and Burt would wait for Fuchs together, but when Fuchs arrived in the anteroom Perrin would go out by the other door, leaving Burt alone to arrest him.
So the following morning, Thursday, 2 February, Perrin telephoned Fuchs at Harwell and asked him whether he would come up to his office that afternoon. Fuchs agreed. He said he would take a train from Didcot that arrived at Paddington Station at about 2.30 in the afternoon, and should be at Shell-Mex House in the Strand a quarter of an hour or so after that. Burt arranged with Perrin to be there at 2.30.
But Burt did not arrive on time. Perrin did not know it, but he was held up because the Fuchs case had already become an international issue. The Foreign Office wanted the US Government to agree to the precise wording of the charge before Fuchs was arrested, and American approval had not yet come through.
Burt was still not there when Perrin’s secretary told him that Fuchs had arrived and was in the anteroom. Perrin was embarrassed, and he told her to say he was delayed at a meeting, and to ask Fuchs to wait. Burt arrived at 3.20. Then Perrin told his secretary on the telephone to ask Fuchs to come in. He slipped out into the corridor, and went into the anteroom as Fuchs left it.
Fuchs had been waiting patiently in the anteroom. He walked into Perrin’s office and found a stranger there. The stranger introduced himself as Commander Burt, a police officer. He told Fuchs that he was being charged with communicating information that might be useful to an enemy in violation of the Official Secrets Act on two separate occasions, and was under arrest.
Now the reality that had been outside Fuchs’s field of vision all along burst upon him. He turned pale, and slumped down in Perrin’s chair. After a while, he asked whether he could see Perrin.
Burt went to the door leading to the anteroom and told Perrin, ‘Dr Fuchs would like you to come in and see him.’
Perrin found an ashen-faced Fuchs sitting at his desk.
Fuchs looked up at him and said, ‘You realize what this will mean to Harwell?’
Fuchs was taken to Bow Street Police Station and spent the night in the cells. The next morning, as required by law, he was brought before a magistrate, Sir Laurence Dunne, at Bow Street Court. Commander Burt testified that he had arrested Fuchs the day before, and stated the charges. Dunne asked Fuchs, as he customarily asked a prisoner: ‘Is there anything you want me to do for you in the way of legal representation?’ If a prisoner cannot afford to hire a lawyer, he is entitled to a court-appointed defence counsel. Fuchs answered, I don’t know anybody.’