Philip Larkin was wrong: sexual intercourse did not begin in 1963; it began in 1956. So did the ’60s, though no one really noticed this had happened until the Beatles released ‘Love Me Do’ in 1962.

It was the year of the invasions of Hungary and Suez, of home-grown British rock ‘n’ roll, of Nikita Khrushchev’s ‘secret speech’ revealing the crimes of Stalin, and of Look Back in Anger and the angry young men. It was – so Tony Russell and I maintain in our book about 1956 – the year in which the world we now live in was born.

Before 1956, women were expected to see sex merely as a commodity to be traded for a wedding ring. In David Lodge’s 1987 novel How Far Can You Go?, Dennis and Angela wait for many years for their wedding, while they get their degrees, he does his National Service, they get jobs and save money. In 1952, he puts a hand on her breast outside her blouse. In 1953, he strokes her leg to stocking-top height. In 1954, he puts a hand inside her blouse and onto her bra.

But the governing class lived by different rules. Sexual intercourse only began in 1956 for the hoi polloi; toffs had had it for years. The early ’50s were remarkably tolerant about the peccadilloes of celebrities and the political and upper classes, so long as they were conducted discreetly.

The same politicians who upheld laws against homosexuality quietly covered up for their colleague Tom Driberg, whose exploits with men were common gossip in the Strangers’ Bar.

It was well known in political circles that Harold Macmillan’s wife had for years had an extramarital affair with Robert Boothby, and that the fourth and youngest of the Macmillan children, Sarah, born in 1930, was biologically Boothby’s child. In the circles in which they moved, it does not seem to have affected the way in which Macmillan, Boothby or Lady Dorothy were regarded.

So sex was, after all, not invented in 1956. It was democratised in 1956, and not without controversy. A few months after the May production of Look Back in Anger, its author John Osborne showed that he could see dimly a revolution brewing in the relationship between men and women – and it was a revolution this revolutionary playwright did not like at all. ‘What’s gone wrong with women?’ he asked in the Daily Mail in November:

‘Never before have women had so much freedom, so much power, or so much influence … It seems very obvious to say that women have arrived, that at last they are coming into their own, but what is not so obvious is the price we are all paying for it.’

Despite John Osborne, the freedom of Tom Driberg to have homosexual affairs, and Lady Dorothy Macmillan to have heterosexual ones, started to spread down for the first time to the middle classes, while the Wolfenden committee worked on its report recommending the legalisation of homosexuality.

Politicians now know they cannot get away with any behaviour that those who elected them cannot. In fact, as we write, politicians are probably judged by harsher standards than any other people today.

1956: The Year that Changed Britain by Francis Beckett & Tony Russell is out 13 October and available to pre-order here.