Patrick Mercer has gone out in style. One Tory MP, hearing that the whips had tried to dissuade him from triggering a by-election fight with Ukip at an extremely inconvenient time for David Cameron, told me:

‘It’s a waste of time. He’s determined to damage Dave. He’s Colonel Nicholson in Bridge on the River Kwai!’

Mercer has left Cameron a little present in the form of this by-election. Even if Nigel Farage announces today that he won’t stand in the contest (and James’s post from last night on the Ukip leader’s thinking is a must-read), Ukip can still repeat its success in Eastleigh by fielding an impressive formerly unknown candidate. In Eastleigh, Diane James was easily the most polished and impressive out of all those standing – and her candidacy helped Ukip give the impression it was more than a one-man band.

One senior Tory familiar with the thinking of the party’s campaign machine says ‘we do NOT want a by-election’. Well, they’ve got one, and whoever represents Ukip in the battle will make it as painful as possible for the Conservatives who have spent months meticulously preparing for the fallout, if any, from the European poll. It is easy to argue that the European elections are just an opportunity for voters to show that they’re angry before returning to more conventional voting patterns in the general election. But even if they’re mostly fought on local issues, as Eastleigh was, they are always read as a bellwether for the mood of the country – and used as a big stick to beat the party leadership.

UPDATE, 8.07am: Farage has announced he isn’t standing in Newark.

Tags: Newark by-election, Patrick Mercer, UK politics