Martin Sherman’s treatment of the lives and persecution of gay men, and the winning of equal rights, is an impressive piece of theatre.

Plays which cover an immense timespan of events are a risk. Put simply, how do you cover many decades of subject matter in around 90 minutes without the plot, script and performances breaking into an unmanageable gallop?

This makes Gently Down the Stream, Martin Sherman’s treatment of the lives and persecution of gay men – and the winning of equal rights – an impressive piece of theatre. Set in London, in the home of ageing cocktail pianist, ‘Beau’ (played by Jonathan Hyde), it centres on his relationship with a much younger man, Rufus, an M&A lawyer (Ben Allen).

Rufus’ initial fixation on the aesthetics and apparent glamour of the age Beau knew first hand – which in the entertainment industry was used to conceal sexuality and sexual meaning from the general public – prompt’s Beau’s recollections of the past. This runs from the relative sexual freedom of World War II New York, related to Beau by an elder lover, to the clamped down intolerance of the McCarthy era and direct memories of violence and AIDS.

Beau and Rufus’s shared time together, covering 13 years, takes in significant legal wins in the UK, including the introduction of civil partnerships and same-sex marriage. Shaped by the pain of the past, Beau’s expectation of unhappy endings for gay men and gay relationships is contrasted with Rufus’s outlook. As a millennial, Rufus has known only the growing tolerance of the cosmopolitan capital and the establishment of welcome legal rights. Coming out was like ‘an unplanned bar mitzvah’, he quips.

In fact, he feels the main reason he is conspicuous is for a close interest in odd subjects – his parents, he remarks at one point, regard him as ‘queer’ not for his sexuality, but because he lacks interest in football.

Hyde and Allen give complex, faultless performances and are well served by the play itself, which prompts tears, laughter and reflection – it finds humour in the serious and the tender.

It is not, though, a simple trot through the progress seen for gay men and couples in the time covered. Beau’s experiences cast a shadow over the idea of progress, implying it cannot be relied upon – leaving the suggestion in the air that preserving progress might be as much a fight as achieving it was.

Gently Down the Stream is at the Park Theatre, Finsbury Park, London until 16 March