It is the year 2021, and Brexit has happened “up to a point”, but people feel nothing has really changed, until Joe Newman, an obscure Labour MP in the north of England, is deselected by Momentum activists, resigns his seat, fights and wins the resulting by-election as an independent, and finds himself at the head of a wildly popular protest movement.

This is the situation explored in Michael McManus’s play, An Honourable Man, being performed this week at the White Bear Theatre in Kennington in south London. It is lent added topicality by the splintering yesterday of the Labour vote, with 15 Labour MPs voting against membership of the EEA and in the Government lobby, for they know the Labour front bench’s line will be regarded as a sell-out in their constituencies, and quite a few of them happen to have highly marginal seats.

Before going to see the play, I spoke to its author, who is known to many readers of this site, for he has long been active in Tory politics, contested Watford in 2001, more recently just missed out at selections in Havant, Spelthorne and Braintree, and has written in The Daily Telegraph about the revival in political theatre.

From as far back as 2004, McManus has “sensed a gathering storm in British society”, with which the two main parties are ill-equipped to deal, because the Conservatives and Labour, pro-European and socially liberal, have more in common with each other than with the wider public.

The further you go from London, the more true this becomes. McManus found it confirmed by spending a lot of time on doorsteps during the by-elections in Stoke Central (now represented by Gareth Snell, one of yesterday’s Labour rebels), Copeland and Sleaford & North Hykeham.

McManus traces the origins of the problem to Tony Blair: “Blair got several things badly wrong. He promised a referendum on the Lisbon Treaty. He promised it and didn’t deliver it. That would have let the steam out.  He also got it wrong on the Polish migration.”

British politics became “a pressure cooker where the valve is shut”, and in McManus’s view, “theatre is a very good place to open the valve.”

Newman, the founder of the Popular People’s Movement, or PPM, almost immediately discovers that if he is to succeed, he needs to come down firmly against immigration. As one of his advisers tells him,

“If you really do want to control your borders – and we all know the voters overwhelmingly do – then you must be willing to do things that can be portrayed as callous or cruel. Turn people away. Forcibly deport people.”

“Well it is what my constituents are telling me,” Newman admits. One may remark in passing that this is what is actually happening in Italy, with the turning away of a boatload of refugees, while in Germany, the issue has divided Angela Merkel from her Bavarian colleague Horst Seehofer, the Interior Minister, who is determined to take a harder line, facing as he does regional elections in which his party is threatened by the anti-immigration party, Alternative for Germany.

Newman is not at all sure he wants to campaign against immigration. He prevaricates, and the woman who is his best friend implores him to be kind. But young Sam, who works in his office, tells him that in order to win over the rest of the country, “you must first declare war on Islington Man.”

We glimpse how lonely it is to be a leader, and especially an unmarried leader. Newman is gay, and as soon as he starts to be alarmingly successful, his opponents leak to the press the story of an embarrassing affair with a younger man. To whom now can he turn for advice?

At one point, he finds himself seeking advice from a ludicrous PR man, to whom he exclaims, “Can’t I just be myself?”

“It’s never been tried,” the PR man replies.

The question of how to be oneself – how to be authentic – is an extraordinarily difficult one. What if the voters don’t want your authentically held opinions, but would prefer you to to adopt some other opinions, in which you don’t believe?

At what point do you cease to be “an honourable man”? – the expression Shakespeare, greatest of our political playwrights, made Mark Anthony use ironically, the irony becoming more deadly with each repetition.

The play is interspersed with news reports, shown on television screens, charting the rise of Newman from his by-election win onwards. So we see John Curtice assessing his chances, and Stephen Pound (Lab, Ealing North) arguing with him on College Green.

These intrusions of the real world (if that is the correct term to apply to political television) are in some cases highly amusing. And Timothy Harker, who plays Newman, makes him seem just like an obscure, essentially decent backbencher, who when catapulted to fame, almost at once finds himself and the people he loves in danger of destruction.

Max Keeble is excellent as Sam, the ambitious young adviser, clever, callow and ruthless, who flies into a rage when Newman shows infirmity of purpose, and tells him he has to carry on, for otherwise, how is he, Sam, going to get to Downing Street?

This is McManus’s first play. I did not feel, as I saw the first night, that I was present at the discovery of a new Tom Stoppard or Joe Orton, but that is a high standard by which to judge a new playwright. An Honourable Man contains many enjoyable jokes, towards the end become unexpectedly touching, and is throughout a good way of thinking about the state of our politics. Life may well end up imitating art.

McManus also has a gift for getting an audience together. The first night was attended by Michael Dobbs and Jeffrey Archer, among many others.