Well, of course Diane Abbott and Jeremy Corbyn had a brief relationship in the 1970s, culminating in a motorbike tour of East Germany. Contrary to some cartoonish idea of the left being principled high-minded activists too busy to shag, everyone had sex in the 1970s, because that’s all there was to do. It was a sign of revolution against the bourgeois fug of respectability, the Mary Whitehouse brigade; and it was a crucial substitute, in a period of two-bar electric fires,and space heaters powered by coin-operated meters, for central heating.

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We’re talking about an era when the concept of dates and dating was some distant, incomprehensible American high school thing involving soda fountains and little deuce coupes. A recent graduate of York University complained to me of the paucity of nightclubs in the cathedral city, and asked what it was like in my day. Nightclubs conjured up the image of couples in evening dress and Brylcreemed hair smoking at tables with lamps on them, while on stage a crooner hugged a microphone. The university left occupied its evenings with meetings then, when they were finally over, reconvened at the pub. At closing time, as you walked off down the street with a bag of chips, a boy might accompany you and indicate his sexual interest by, say, putting a comradely arm around your shoulder.

Sex was the reward for attending all the endless meetings, or the natural consequence of all that sitting, in the days when the word gym meant the room at school with wall bars. There were problems about staying up too late (everything shut by 10.30pm anyway), but there were early-morning duties for the committed comrade: trying to sell copies of Socialist Worker outside the gates of the local factory to shift-workers.

Only with “the benefit” did the social life of the left take a notch up into something resembling a kind of festivity. The benefit was a disco. It would be in aid of one of the great causes of the day, the Nicaraguan Sandinistas, Troops Out (of Northern Ireland), the miners, the steelworkers, the Anti-Nazi League; clumping round the floor to Tom Robinson in nothing so hierarchically exclusive as couples but ragged groups of girls and boys. Refreshments would be served: cans of Party Seven beer, 50p bottles of Hirondelle (a sweet white wine), French sticks and blocks of orange Red Leicester. Occasionally exiled Chilean leftists would turn up with a Tupperware box of empanadas.

For a period in the early 1980s political lesbianism overtook shagging for the revolution

One of the tactics the various left groupuscules used to expand their membership was known as horizontal recruitment – which, as its description implies, sought to lure potential new members into the sect with a shag. There weren’t quite enough existing members at any one time to go round, and it was easy to quickly exhaust all the available sexual partners, so ongoing expansion was vital.

Nonetheless, there were continuing controversies about love, not across class lines but rather those involving the International Marxist Group, which considered the Soviet Union to be a deformed and degenerate workers’ state, and the sharply contrasting International Socialists (later the Socialist Workers party), which regarded the Soviet Union as an example of state capitalism dominating its satellites. These Romeo and Juliet situations were tolerated, though it was less acceptable to cross a red line and shack up with someone from a rightwing organisation such as the Communist party.

To some extent the women’s movement would put the damper on the idea that the left was a pool of liberated chicks willing to unencumber boys with lapels sagging with badges of their unwanted virginity. For a period in the early 1980s political lesbianism overtook shagging for the revolution: the idea that if you were a real feminist you would only sleep with women, a stance that Beatrix Campbell sarcastically observed replaced the whole point of being gay – sex – with ideology. One might move then towards asserting that one would sleep only with women of colour in an act of solidarity, until women of colour said their real solidarity was with men of colour. Awkward, as the young say today. You started to think that more time was being expended on talking about the correct principled position on sex than actually having any.

I suppose all this must have eventually dropped away as people got jobs, formed long-term relationships, tempered their political convictions. Looking back, I sometimes read a familiar name in the newspaper and wonder: “Did I sleep with him? Yes, I think I did.”

The revolutionary past revives itself from time to time at moments of national emergency, as happened to friends who took up their banners and went on the 2 million-strong 2003 march in London against the Iraq war. On running into some old neighbours from back in the day, they peeled off and went for afternoon tea at John Lewis, the Place to Eat.

Linda Grant’s novel of 1970s university life, Upstairs at the Party, is published by Virago