Nobody mainstream (except Yahoo News) seems to want to report on this so far - can't think how the BBC missed it though
I haven't seen any estimate of numbers of protesters, but speaking as one who was there, I would guess several tens of thousands. No violence though so perhaps not worth reporting.
The Metropolitan Police were models of impassive propriety, although they were out in some force outside Downing Street and to a lesser extent outside the BBC. They did have van-loads of reinforcements parked just off the route in case of need, but they stayed out of the way.
A good day for all concerned.