John Biffen was mentally ill. This is the outstanding revelation of Semi-Detached, a memoir which has been assembled from his diaries and from the autobiographical writings which he completed before his death in 2007. During the mid-1960s he tried psychotherapy, which he described as ‘lugubrious’, ‘painful’ and ‘not a cure’. He got far better treatment from a Harley Street specialist, Peter Dally, who regulated his lithium doses with blood tests and improved his health to the point where he felt able to join the shadow cabinet in 1976. He served as Trade Secretary under Mrs Thatcher and later as Leader of the House.

Biffen loved gossip. He reports a lunch meeting between Lord Windlesham and Ted Heath shortly before the 1979 election, during which Heath revealed his expectations of a political comeback. He would accept the chancellorship, he conceded, but not the Foreign Office, which was beneath his dignity. His great hope was for a Conservative defeat which would pave the way for a second bout of his leadership.

The star of Biffen’s book, albeit in a cameo role, is Mrs Thatcher. According to a popular myth which appears to strengthen from day to day, the Iron Lady was a stateswoman of dazzling intellect and heroic selflessness, who miraculously combined the chief virtues of Moses, Adam Smith and Mother Teresa. That’s not how it seemed at the time.

Conservative MP John Biffen Photo: Getty 

In the early 1980s, her cabinet colleagues were already complaining of her ‘emotional and vindictive tactics’. Biffen himself was shocked to see her belabouring senior civil servants as if they were ‘recalcitrant schoolchildren’. At the height of the Falklands crisis he records ‘an ugly display of megalomania’, during which the PM contrasted her ‘rock-like qualities’ with those of ‘her India-rubber cabinet’. The following year Geoffrey Howe suggested in the mildest terms that a diplomatic rapprochement with Argentina might be possible. ‘She blew up,’ Biffen reports, ‘and treated us to a horrifying display of paranoia. Michael Havers [the attorney general] is deeply concerned by it.’

In 1986, Howe and Biffen lamented her ‘bossy and intemperate manner’ towards Michael Heseltine, which led to his ‘needless alienation’ over the Westland crisis. ‘Needless’ is significant because it was the Westland affair that drove Heseltine from the cabinet and ultimately triggered Thatcher’s demise. In the same year Willie Whitelaw emerged bruised and chastened from one of her more enthusiastic verbal pummellings and predicted that she would ‘take the Tory party under’. Spot on, Willie. Twenty-eight years later the Conservatives have yet to resurface.

Biffen devotes a separate chapter to Mrs Thatcher which is more generous and balanced than the impression given by his contemporaneous notes. He praises her pluck and determination and cites her kindness to her personal staff, one of whom, named Ethel, was a keen supporter of capital punishment. Thatcher enjoyed teasing the cabinet at working breakfasts. ‘All this crime: Ethel says, “String ‘em up.” ’ Her colleagues must have been quaking over their croissants because Thatcher had a habit of unearthing dated and unworkable policies and converting them into political totems. The poll tax, to take the obvious example, is dismissed by Biffen with magisterial brevity. ‘She called it her flagship. I called it the Titanic.’

His downfall came, quite by chance, after a TV interview given in Birmingham following the local elections of May 1986. The Tories had taken a pasting and Biffen chose to be candid with the viewers. These words killed his career:

Nobody seriously supposes that the prime minister would be prime minister throughout the entire period of the next parliament.

Back in London he noticed that ‘a curtain had come down’. Thatcher’s press secretary, Bernard Ingham, described Biffen as a ‘semi-detached’ member of the cabinet. Asked to respond, Biffen used a more forthright metaphor. ‘I said I thought Ingham was the sewer not the sewage.’ As soon as Thatcher secured her third victory in 1987, Biffen got the boot. Yet he acknowledges his debt to Ingham for providing a title for his book.

It’s rare to read a political memoir so untainted by malice or self-justification. ‘The most loyal and straightforward of men’ was the verdict of Brian Walden, who conducted thefateful television interview. Biffen’s thoughtful, conscientious, self-effacing and unerringly honest character shines through every page. The puzzle is, how on earth did a man like that ever end up in Mrs Thatcher’s cabinet?