The Tories’ Henley by-election candidate, John Howell, has been caught with briefing notes apparently aimed to help him appear “normal”, with information about the cost of basic produce in the supermarket – a revelation surely more damaging than just admitting you don’t know.

It’s an amusing insight into the Conservative campaign, but its exposure by the Liberal Democrats reminds me of one of the most memorable incidents in the 2006 midterms, when soon to be ousted Virginia Senator George Allen was caught using the slur “macaca” against an opposition activist.

What made a big difference to the impact of Allen’s comment – and the ability to prove what he’d said – was that the incident was caught on video. It suggested a new type of campaigning, where activists follow their opponents around hoping to catch a similar error.

This step change hasn’t happened – and with limited resources, campaigns sensibly use these on methods with clear benefits, rather than risking waiting for a slip-up that never comes. In the case of the John Howell incident, it looks like the photographer was in the right place at the right time. But the thousand words of a photograph are far more effective than a verbal claim about what was spotted. It should serve as a reminder to politicians that modern – and not so modern – technology can catch even the smallest revealing mistake in amber.