David Willetts is standing down at the next election. He is 58.  So Andrew Lansley. He is 58, too.  So is William Hague. He is 53. So is Greg Barker. He is 48.  And now we learn that Hugh Robertson is also to leave the Commons.  He is 52.

Unlike Hague, Sir Hugh is not a nationally-known politician.  And unlike, say, Willetts, he was not entitled to attend the Cabinet when he served in government.  But he was a mainstay of organising the Olympics while he was Sports Minister.  He is a capable, intelligent and – now – experienced politician.

Not so long ago, more former Ministers stayed in the Commons, thereby giving it the benefit of their knowledge.  “We tried that in Government,” one might say of a proposal.  “And it didn’t work.  Here’s why.  But this is how it could.”  And so on.

In losing people of Sir Hugh’s quality, the Commons is losing this knowledge, experience and (I would go so far as to say) wisdom.  So why is he leaving?  He says that this “is realistically the last opportunity to move on”.

I don’t know his plans or indeed any more.  But it is certainly the case that some former Ministers feel that it is increasingly difficult to be an MP and to have outside interests.  This is regrettable: a chamber of professional politicians will have little wisdom at all – especially if the drop-out rate rises further.

The Commons can’t afford to lose people like Sir Hugh.  But some former Ministers feel that they can’t afford to stay.  Perhaps they should count their blessings: MPs are in the top three per cent of earners, after all.  None the less, the shift to professional politics isn’t helping the Commons – or anyone else.