Sometimes you watch a politician say something and instantly get a preview of a future election campaign – particularly when they’ve just said, on camera, something which will be used against them again and again.

Tim Farron offered just such a hostage to fortune today at the Lib Dem conference.

His pitch to Labour voters was that his party would give the NHS more money, even if it meant higher taxation. Indeed, he said he’d consider a dedicated NHS tax. That in itself might not present a problem – as long as you phrase it so that any clip must feature the specific argument about funding the health service.

As it was, a rather naively written script offered anyone seeking to criticise the Lib Dems an easy, punchy stand-alone clip pledging simply that “Liberal Democrats will raise taxes”. Indeed some are already using it:

Should he ever present a sufficient electoral threat to merit attack ads, you can be sure this will be wheeled out.