In 1974 Harold Wilson telephoned me in the afternoon of the day before he was appointed Prime Minister and asked me to come to his house in North Street. He began the conversation by saying that he expected to be called to Buckingham Palace the next day. He then stated that he had decided to accept this office for a period of two years at the utmost. I asked him the reasons and he replied that there were medical and personal reasons that made it impossible for him to retain this office as Prime Minister for longer. He told me that even with a short period he had been "the longest-serving Prime Minister". He said that he could not carry the "burden" any longer.
After the Prime Minister had taken office he invited me to a private luncheon at Downing Street. I was again alone at this meeting. After lunch he invited me to come to his study. When we arrived there it was found that the key for the study could not be traced. He had therefore not used this study before, and after waiting for about 15 minutes, the key was produced. As we were settling down in Mr Heath's study he looked around the room and said, in a joking way, "You can talk quite frankly to me in here. There is only you, I and MI5 listening," pointing to a hole in the wall where some picture had been previously removed.
Within a month of Harold Wilson's appointment I happened to meet his doctor, whom I knew fairly well. He committed no indiscretion but gave me a hint as to his medical condition. Prior to this meeting I had always admired Mr Wilson's fabulous memory and it was already clear to me, when I spoke to Harold Wilson this time, that his memory was very good but as was apparent from previous discussions, not as accurate.
I strongly believe that Harold Wilson's preoccupations with MI5's investigations were somehow connected with his progressive medical state. I think Harold Wilson was very intrigued with MI5's interest but had an ironic attitude towards it. He always considered them as being a somewhat ridiculous attempt to unsettle his position. I can never remember an occasion when he mentioned these facts without a smile .
He resigned exactly on the date he had told me.
House of Lords