While the entire regiment of political reporters continue to pursue the non-story of the non-rebellion against Ed Miliband, based mainly on them repeating their own abuse of Mr Miliband and then producing this abuse as evidence of the fact that he is useless, a real story took place.

In this development, there is a fact. And it is an amazing fact, worthy to head front pages and lead bulletins. The leader of the Tory Party so fears losing a by-election in a seat formerly held by his party that he is appealing to Labour voters to save his candidate from defeat.

He went on to ask Liberal Democrats and Greens to back him too.

This wasn’t an unsourced leak from a ‘friend’, or a unnamed plotter, nor was it a claim of what somebody had said which couldn’t be confirmed. This was the Prime Minister, on the record. He can have had no doubt of the significance of what he was saying. His very presence in Rochester is a breach of what used to be an absolute convention, that party leaders did not take part in by-elections. The idea was that, if they were personally associated with a defeat, their leadership would be in question. Well, by any rational calculus, Mr Cameron is one of the most unsuccessful and bungling leaders the Tories have ever had, but he is immune to the effects, which is perhaps why the entire regiment of political reporters chases after Mr Miliband. It is a sort of displacement activity.

Here is what the leader of the Conservative and Unionist Party told the Kent messenger:

‘You can vote for UKIP and be part of the national campaign and another notch for them in their development and then the great caravan will move on, or you can vote for Kelly, who is a hard-working person, born and raised locally.

‘I would say to people who have previously voted Labour, Liberal, Green or anything, that if you want a strong local candidate and don’t want some UKIP boost and all the uncertainty and instability that leads to, then Kelly [Tolhurst] is the choice.’

How it must have choked him to mention UKIP at all, after his long and mistaken attempt to get rid of them by ignoring or deriding them.

Now that this has failed, he has actually declared that UKIP are the common enemy of Tory, Labour, Lib-Dem, and Green Parties. And that the Tories have more in common with Labour, the Lib-Dems and the Greens than they do with UKIP.

Well, I have long known and said that this is the case. But you no longer need to take my word for it. Mr Cameron has confirmed it. I do hope the voters of Rochester and Strood will take note next Thursday, and the voters of the whole country will take note in May. There has never been such a clear statement of the choice – all the establishment parties on one side , UKIP on the other.