'Upgrading' to skinny tyres pointless for London commuting

Giro Tech: Rise of the 25c tire
In the last year or so that thinking has begun to change. Here at the Giro, the 23c is in decline, replaced by its slightly fatter cousin, the 25c. Many of the teams already recognized for more progressive technological mindsets have begun using fatter 25c tires for regular road stages – no cobbles or gravel in sight, just smooth(ish) Italian tarmac.

http://velonews.competitor.com/2012/05/news/giro-tech-rise-of-the-25c-tire_218011