TO swim in the murky whirlpool of 24-hour news, political leaders increasingly feel the need to appoint spin doctors from the other side of the fence.

Tony Blair had Alastair Campbell.

David Cameron had Andy Coulson – both with tabloid backgrounds and a wealth of understanding about the workings of the modern media.

But recruiting a former poacher as a gamekeeper is always going to be a gamble. They may know the tricks of the trade, but they come with baggage.

To have succeeded in the ultra-competitive world of the national tabloids, the likes of Campbell and Coulson must have engaged in cut-throat activities at some point in their careers.

When Mr Cameron chose Mr Coulson as his communications chief in 2007, it was a risk. A month earlier, he had resigned as editor of the News of the World, denying knowledge of, but taking “ultimate responsibility” for, a phone hacking scandal which led to his royal editor being jailed.

The bad smell has lingered ever since. Could the editor of a national tabloid really have been oblivious to the unethical techniques used by his staff to obtain scoops?

Frankly, I doubt it and it is a question which understandably refused to go away, to the point at which Mr Coulson finally resigned yesterday.

It leaves legitimate questions about whether Mr Cameron should have stuck with Mr Coulson for so long – and indeed whether he was wise to appoint him in the first place.

The gamble backfired.