It’s thought 80 per cent of all UK bike thefts occur in London – a figure estimated to be 20,000 a year, although the true number could be four or even five times that.

… Bike registration schemes sound like a good idea, but the benefits are slim – after all, cars are identifiable by their registration plate, VIN number, serial numbers and the ECU and yet only about one in four stolen cars is reunited with its owner.

Quite apart from the fact that bike registration marks can be removed by thieves, these schemes assume stolen bikes remain within our borders. According to research in The Netherlands bicycle theft is increasingly committed by organised gangs who often export them.

https://www.eta.co.uk/2023/03/10/how-do-we-solve-a-problem-like-cycle-theft/