There is barely a sitcom from the past 30 years that doesn’t owe some sort of debt to Cheers. Premiering in 1982 and running for 11 seasons, it invented or perfected many of the genre’s most recognisable conventions. Story arcs. Cold opens. The workplace-as-melting pot format of its titular Boston bar – refined from time spent by co-creators Glen and Les Charles, along with director James Burrows, on 70s comedy Taxi. Most famously of all, it introduced us to Sam and Diane: the original sitcom will-they, won’t-they? couple who, over the course of five mostly wonderful seasons, popularised a whole new kind of romance – before discovering its limits.

The courtship of Sam Malone and Diane Chambers crackled with an electric – and often hilarious – sense of combativeness. He was the womanising jock who owned a bar (Ted Danson); she was the intellectual waitress with delusions of grandeur (Shelley Long). Their attraction, played out over Cheers’s first run of 22 episodes, enraged them both. “You disgust me! I hate you!” screams Diane before their long-awaited first kiss. “Are you as turned on as I am?” asks Sam. Diane: “More!” Sam: “Bet me!”

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But Cheers was too smart, too ahead of its time, to play such dysfunction entirely for laughs. Hence the end of season two, in which the couple, having now been together for many months – Diane depressed from Sam’s selfishness; Sam maddened by Diane’s condescension – explode in one of the show’s most dramatic scenes: the shocking moment Sam slaps Diane. The jokes stop. The studio audience falls silent. It could almost be theatre – a play on the thin line between love and hate. Diane leaves. Perhaps that should have been the end of it. But sitcom logic demanded that Diane return in season three – with a new lover in breakout character Frasier Crane – to once again question her destiny with Sam. Less “will-they, won’t-they?”, more “they already did, will they again?”.

From the copycat romance of Moonlighting in the mid-80s to Ross and Rachel in Friends, it’s a problem that has dogged sitcoms since: how far you can stretch a couple before they edge towards tedium? At the end of season three, Diane jilts Frasier at the altar; at the end of season four, Sam asks Diane to marry him and she (belatedly) says no; by season five, the strain is obvious: with Diane now backtracking on her refusal and suddenly pursuing Sam. It’s here that Cheers suffers one of its worst episodes: Chambers vs Malone, in which Diane – by this point written terribly – takes Sam to court on a trumped-up charge for assault, and forces him to propose to her.

It’s little wonder that Shelley Long, who had grown tired of her repetitive storylines, quit soon after. Although in true Cheers-style, she does leave in one of its most moving episodes: I Do, Adieu, in which Sam realises that Diane would never be truly happy as his wife. Cheers, after all, always knew how to recover from setbacks. It was sturdy, consistent, familiar – a place where everybody knows your name.