Also I reckon statistically it's a normalish amount. If I get a puncture once a year on the way to work thats 1 in 300 chance. Multiple that by 25000 riders and there's going to be a lot of flat tyres.
I did see a guy on a Halfords special arriving at the top of Leigh hill with two flat tyres looking absolutely dejected. Appparently he'd already fixed them earlier on the ride so @hamrack's theory seems legit
Also I reckon statistically it's a normalish amount. If I get a puncture once a year on the way to work thats 1 in 300 chance. Multiple that by 25000 riders and there's going to be a lot of flat tyres.