Main event when PM comes West

Not for the first time has David Cameron's attention been diverted when visiting the Westcountry, writes London Editor Graeme Demianyk.

Yesterday the Prime Minister was in Plymouth, home of Western Europe's biggest naval base, Afghanistan heroes and a substantial commercial dockyard. Defence of the realm, valour and jobs. The Holy Trinity for a Conservative Prime Minister.

But Devonport dockyard was 250 miles from the political centre of gravity at 10am yesterday, when all eyes were on the Crown Prosecution Service's headquarters in London. It's not every day Mr Cameron will get a "Dear Prime Minister" letter – signifying a ministerial resignation – from one of his Cabinet. Yesterday's missive, dashed off by Energy Secretary Chris Huhne amid allegations of perverting the course of justice, was his third.

Cucumber cool, the Prime Minister barely batted an eyelid. "I think Chris Huhne has made the right decision, given the circumstances," Mr Cameron insisted.

Job done. Back to the glad-handing. But Mr Cameron must be used to things not going entirely to plan when Devon and Cornwall enter his diary. Last summer, a family holiday to North Cornwall was interrupted as euphoric Libyan rebels swept into Tripoli. That's what happens when you chair the National Security Council. A day later, though, he was back buying locally caught scallops from a Port Isaac fishmonger.

A year earlier, the diversion was more domestic: the early arrival of the Camerons' fourth child, Florence Rose Endellion, the girl with the Cornish middle name.

Harold Macmillan's possibly apocryphal saying – "events, my dear boy. Events" – seems to resonate when Mr Cameron visits the far South West.