I too have noticed a paucity of witnesses with their trollies in London. Previously noted them regularly at Oxford Circus, Marble Arch, Egware Road, and Victoria Street. I also noted that they tended to funnel - that is stand at side of trolley with arms extended holding out literature. This means that pedestrians' space on pavements was reduced. I am reasonably sure complaints were made to Westminster City Council and that the municipality's response has meant that the Britain Branch has had to cool down their "Metropolitan Witnessing" as they call it. I'm pleased to note their substantial absence - see them as mere litter!