What shall I wear for the London marathon?

My entry has been accepted for the 2009 London marathon, 26 years after I first tried to get a place (one year for each mile – there’s symmetry for you). I’d become so accustomed to failure in the annual ballot for Britain’s biggest road race/fun run (delete as applicable) that I didn’t open the blue shrink-wrapped notification missive until a couple of days after it arrived. And now, having done so, my reaction has shifted almost unblinkingly from ‘Wow, at last!’ to ‘Oh shit, now I’ve got to run it!’ to ‘Bugger, that’s really messed up my plans for next April!’

The thing is that I’ve already booked myself in for a race that I’ve been harbouring fantasies of winning on the day before the marathon. Well, maybe not winning, but, you know, doing quite well in. With 30,000 runners otherwise engaged in their pre-London preparations, there’s clearly no better time to go for gold than against the greatly-narrowed field that will turn out for the Clandon Park 10k near Guildford on 25 April. Now the day will have to be taken up with sorting out what I’m going to wear on a 26-mile jaunt around London instead. After waiting more than a quarter of a century for the opportunity it has to be something special. Any suggestions?