The current Mayor, whilst still a proponent, likely does not use it. A quick glance at the social media that he recieves will tell you why - it would not be safe. He needs to travel with close protection officers.
The reason? He is Muslim, and Britain has become a very racist country indeed. Well, maybe always was, but the likes of Farage and Musk have so emboldened them that there is no longer a stigma.