Take your walking stick and shove it through their spokes mate, that will stop them (very quickly and usually with a dose of pain thrown in for free
)
That or ask our community warden to do something about it, (Oh, forgot, we don't have them anymore do we!!!!)
In that case grab a copper and drag him down to broadway and stand there whilst he does his job. Oh, sorry, you need to find one first and its no point ringing the cop shop, I waited over an hour for plod to turn up to an assault I witnessed.