A little context. On Thursday, Ukip is competing in two by-elections: Clacton, Essex, and Heywood & Middleton, Greater Manchester. On Tuesday Mr Farage was campaigning in Heywood. It just so happened, he explained, that a local supporter owned a private collection of ex-Army vehicles, and the supporter had invited him to pay a visit. So naturally Mr Farage had in turn invited the media to accompany him. This was, after all, a superbly literal opportunity to demonstrate that Ukip was parking its tanks on Labour's lawn.