Filtering itself is not illegal. Even undertaking (overtaking on the left) is perfectly legal now.If you filter or undertake it is for the police to prove that your standard of riding fell below what would be considered acceptable. It will be DWDC if you weave from lane to lane, suddenly cut across the front of vehicles, or ride too aggressively between them.So filtering on its own cannot be DWDC. If you ride smoothly and safely, do not take risks, and do not compromise the safety of others then you shouldn't have a problem. Speed does not make any difference here.If done sensible it is ok for example this chap
Cops I've spoken to about this subject and other things bike related have always quoted "you must be able to stop on your own side of the road that can be seen" so in general terms, if it's deemed that you can't when your filtering and an accident prevales, guess who's at fault? Regardless of the cage driver turning into your path as you filter Law is an ass really.
Am I the only person to have knocked down two people when filtering on 2 separate occasions in 2 different towns
Acually cops do not have any word whatsoever on the legality of filtering. They can do you for dangerous driving, but again nothing to do with filtering per se which is perfectly legal. London cops are pretty relaxed about filtering. Anyway if there is an accident thankfully not the cops, but the court decides who is to blame