Could Dominic Grieve’s Brexit amendment launch a new party?

Inside the Dominic Grieve amendment carried on Tuesday is the embryo of a new political party. Any parliamentary majority for what Sir Oliver Letwin, who voted for the amendment, calls ‘something real’ (‘Norway plus’) if Mrs May’s deal falls would depend on the support of a good many Labour MPs. After three months’ work, the organisers believe they have got 75 such on board, led by Chuka Umunna. These are anti-Brexit, chiefly Blairite Labour MPs who cannot bear Jeremy Corbyn. If their number held up (a big ‘if’), the organisers calculate, the House could carry ‘Norway plus’, with the government and most Conservative backbenchers supporting, even if the ‘hard’ Brexiteers opposed.

Labour would be split. We have sort of been here before, in 1971, when the Jenkinsite, pro-European wing of Labour defied its party’s line and carried Edward Heath’s Bill to enter the EEC. This led slowly to the creation of the SDP.