WE’RE becoming blasé about momentous days in British politics, but yesterday could have been one: seven MPs left the Labour Party.

Brexit is an issue – they all support a second referendum – but there are several other powerful motivating factors.

In a way, the splitters are very brave. Chuka Umunna once had leadership aspirations but now he can never lead a party he has left.

In a way, they are foolish. History suggests that Britain’s electoral system has been two-party for centuries so they cannot win at the ballot box. They would have been better remaining with the many unhappy Labour MPs who are hoping the Corbyn tide is going out and that one day they will regain their party.

An alternative view of history is that the Social Democratic Party split of 1981 precipitated the fall of the left-wing leader Michael Foot, the expulsion of Militant and the slow return of the party to the centre ground.

These, though, are not the 1980s, and Brexit does not allow that sort of long game.

One way for the country to escape its current quagmire is for the party system to break down completely and for new groupings – probably favouring a “soft Brexit” – to emerge.

The Tories are already broken. If some of their rebels quit to join the new grouping, yesterday could have been truly momentous as it heralded the start of a 21st Century reshaping of British politics.

Many people, fed up with endless Brexit, may hope so, although yesterday may just turn out to be a self-sacrificing footnote.