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

same here. 3 years ago I broke my shoulder when i slipped in the rain on a double metal cover strategically positioned in a curve. I was stressed, in a rush and not fully focussed on that day.