Reviving Peter Nichols’s landmark play of 1967 could hardly be better timed. It was only last month that the Privates on Parade author died.

And yet despite all the goodwill attached to wanting the best for a recently deceased writer’s reputation the first half of Simon Evans’s starry production featuring Toby Stephens, Claire Skinner and Patricia Hodge, is almost fatally dated.

Stage and screen (currently in Lost in Space) star Stephens has always had the bearing of a leading man. But as state school teacher Bri he is every inch the unglamorous also-ran.

In his coffee-stained shirt, Stephens has the world-weary demeanour of a man worn down by the unruly students of 4D, a class whose very name is somehow redolent of stamina-sapping comprehensive-school disobedience.

Yet it is not his students who have worn down Bri, but rather life as a parent of severely disabled, wheelchair-bound daughter Josephine (affectingly played by Storme Toolis, who has cerebral palsy).

And despite the support and infinite stoicism of his wife Sheila (Skinner) it is a life that has taken a toll on the marriage.

Josephine’s ability to move is restricted to spasmodic extensions of her arm, while emotions are conveyed through outburst of wordless exuberant sounds or the silence of tears rolling down her cheeks.

Nichols knew what he was writing about. His daughter Abigail was disabled and died at the age of 11, a year older than Josephine in the play.

The first sign that there are elements of the play that have not aged kindly is the brand of gallows humour that Bri has developed. He regularly segues from conversation into the character of a TV reporter or old-school newsreel announcer like a man who has watched too much Monty Python.

There is so much of this, one can only infer that the purpose is not only to convey one of the mechanisms by which Bri — a frustrated artist— copes with the pressure of being a carer, but to entertain the play’s audience, too.

It was probably funny when the play was first seen, but, delivered by Stephens in the hangdog manor of Tony Hancock, the heavy irony lands embarrassingly flat. Also somewhat dog-eared is the use of direct address with which Bri and Sheila act out tableaux from their past — their encounters with unsympathetic and incompetent doctors.

But the second half, which sees the couple visited by wealthy friends Pam (Lucy Eaton) and Freddie (Clarence Smith) and Bri’s emotionally remote mother Grace (an almost unrecognisable Hodge) feels like it was written by a seriously fine playwright at the top of his game.

The language of the time — unfiltered by today’s sensibility when it comes to talking about disability— lands with shocking force. Take well-intentioned Freddie, who advises Bri and Sheila to have another baby so they can have a “proper working child”, the kind of sentiment that it is only possible to think rather than say out loud.

In that sense it is a brave revival. Though no braver than Nichols’s ground-breaking decision to place a disabled character centre stage, write candidly about a subject that was taboo at the time, and with an honesty that rejects every temptation to be sentimental. No wonder the play is a classic.