It would appear that another company, which has routinely flouted the parking regulations in order to trade, reckons that if they continue to contravene the rules they'll be rewarded with a legitimate pitch too. (I'm assuming, quite possibly wrongly, that the vans are unrelated to Piccadilly Whip)
Here's the first of the vans on the bridge the other day
and here's the second, just by the Piccadilly Whip on-pavement stall
I wonder if TfL could arrange for one of Boris's new Routemaster replacements to undergo a crash test here?