Here's the problem: if you ride on the side and there's not enough space drivers will come very close to you or try to squeeze past in between oncoming traffic.

Here's the problem: if you ride on the side and there's not enough space drivers will come very close to you or try to squeeze past in between oncoming traffic. If you ride too close to parked cars you are liable to get doored, which has happened to me (in Kensington of course, by some upperclass twit stepping out of a cab who's probably never ridden a bike or driven a car, but I digress). A friend of mine almost had his trachea punctured by the corner of an opening door. So, no, if there's not enough space, cyclists should absolutely get out in the middle where cars can see them and respect them. That said, London rush hour is not a place for slow or casual cyclists unless you really know your routes through side streets. We're still a long way from Holland.