Canary, Hampstead Theatre, London

Taking its title from a comment by gay activist Peter Tatchell (“We’re the canaries in the mine”), Jonathan Harvey’s new play sketches 50 years of gay history in England. Russell (Sean Gallagher), a Simon Cowell-esque TV entrepreneur, has turned up at the house of Tom (Philip Voss), a grizzled police chief, to the dismay of his wife Ellie (Paula Wilcox) and the amazement of his teenage daughter, Melanie (Jodie McNee), who demands to know why the press are camped outside the door. Tom’s shameful past is catching up with him.

But the initial scenes are muddled and choppy and stridently overacted. The staging is unambitious and countless short scenes mean there are too many distracting scene changes: a hospital bed wheeled on and off, chairs and tables and props carried on and whisked away. The juggling of past and present, frequent doubling of roles and the fact that Tom and Russell are played by two actors apiece (Ryan Sampson and Philip McGinley play the younger versions) all add to the confusion.

The clichés don’t help either: “You’ve got to be strong for me!” “I wish I could stay like this for ever.”

Ben Allen is poignant as Mickey, Tom and Ellie’s tragic gay son. Another strand involves Billy (Kevin Trainor), young Tom’s pre-marriage lover. In a horrific scene, he undergoes aversion therapy to “cure” his sexual orientation. In the first half, only this scene and another, where Billy rains down love letters from the church balcony during Tom’s wedding, are visually inventive.

But, in the second half, the story magically coalesces and the writing tightens. Voss camps it up as Mary Whitehouse at a Christian rally while the cast members, sitting among the audience dressed as nuns or in drag, stage a raucous demonstration. Paula Wilcox does a droll turn as Margaret Thatcher, debating condoms with her health minister Norman Fowler, and Harvey crafts scene after scene of passion and revelation. He tries to stuff too much in, but it’s a generous fault. And in the end you can’t really dislike a play that has Wilcox in a fur coat flying through the air on a wire.

www.hampsteadtheatre.com