Actually it is. Around 2005 I was stopped by police at 2am in Hackney and told in no uncertain terms that it was illegal for me to be walking with a 2x4 in my hand
Yeah, today you would stopped and frisked, detained, photographed, fingerprinted, interrogated, and finally jailed… for speaking out against the asshats who the think this is a good law.
It was added as context for why someone might be carrying a wooden plank at 2 in the morning and why police might be concerned. It is my understanding that Hackney has changed dramatically in the intervening years