Joan Smith: A man who does his thinking in the park is not all bad

To find a British politician comparable to Letwin you have to go back to the late Sir Keith Joseph

I know I should think it's absolutely dreadful and call for an inquiry. But I love the idea of a government minister ambling through St James's Park on his way to work in Downing Street, discarding a memo here and a letter there. Even my elderly mother has a shredder these days, so the sight of Oliver Letwin tearing up pieces of paper in the old-fashioned way is curiously charming.

Yes, I'm aware of the risk of identity theft and I can imagine that an MP's constituents might not be very pleased if their correspondence turned up in a Westminster litter bin. But it's not exactly a hanging offence, is it?

Letwin is the Cabinet Office minister for policy, which means he's in the happy position of being paid to think. He's an intellectual, which is rare in public life these days, and I expect he takes a balanced view of the usefulness of most official documents to al-Qa'ida, always assuming that they have operatives sifting through litter in royal parks. It's hard to imagine David Cameron making such a gaffe, but then he's a PR man, who used to go in for man-of-the-people stunts like cycling to work from Notting Hill (the briefcase followed in an official car, remember).

Actors do better in politics than intellectuals, a circumstance proved by the contrasting fates of Ronald Reagan and Michael Ignatieff. While Reagan graduated from starring in not-very-good films to become president, the undeniably clever Ignatieff resigned as Leader of the Opposition in Canada after a catastrophic election defeat earlier this year.

I know diehard Brownites who swear that Gordon Brown's really a frustrated intellectual, but my view is that his judgement is too clouded by emotion to qualify. Robin Cook is the nearest thing Labour's had in recent years, displaying an independence of mind and enviable grasp of detail, but that didn't make him popular in the House of Commons.

To find a British politician comparable to Letwin you have to go back to Margaret Thatcher's mentor, the late Sir Keith Joseph, who attracted a similar reputation for being not entirely practical, shall we say. To be fair, I don't think either of them is as unworldly as the well-known historian who once sat on me at a party, apparently failing to notice I was already occupying the point he coveted on a sofa. But what Letwin and Joseph have in common is intellectual curiosity and a lack of concern about how they look to other people, which stands out at a time when politicians live in fear of upsetting constituents.

Joseph described himself as a "convenient madman" but today he'd be stuck with that dreadful label "blue skies thinker", and get the PM into no end of trouble. According to a former researcher, Joseph once commissioned a paper on the moral case for child labour, not because he approved of it but as an intellectual exercise. I also heard a story about someone inviting him to an editorial lunch and contacting his office to ask if he had any dietary requirements; the unexpected answer was that "the minister eats only boiled eggs".

Members of the public often complain that MPs are insincere and afraid of speaking their minds. But they don't much like it when politicians tell them they're wrong or come up with unorthodox ideas. Even a walk in the park can be dangerous, although David Cameron is probably wishing his erstwhile defence secretary had taken a morning stroll weeks ago and discarded his unofficial adviser in the nearest bin.