So who's actually taken a tumble in London then?

Never ever turn your front wheel while going over a drain/manhole/anykinda metal cover. I learned that lesson very very early on in my cycling career and it was one I never needed to be given again

Toronto (and other cities) has the lovely feature of street car tracks. Dangerous in any condition, deadly in the rain/snow (covered with snow!). Every time going over you really have no way of knowing how it's going to end. Of course, 99% of the time nothing happens, but all your muscles (involuntarily?) stiffen when going over in anticipation of what could be.

I think I saw some old street car tracks in London recently?