Doug wrote:
For several days now there have been moderate pollution warnings but
today, Friday, this has turned to 'High' and people are advised to
stay indoors. So cyclists beware and we can thank the many motorists
on our roads for contributing to that harmful pollution.

the air quality monitoring thingy shows all of London as green, so all ok
actually:
http://www.londonair.org.uk/london/asp/default.asp