Not the best deterrent, this is in a gym car park so obviously a vehicle involved ,
as for D locks , I had a distress call a young lad had lost his keys so I went along and it took 2 mins or less to cut off with my grinder and a s/s cut off blade, no passers by took any notice .
As for busy area , my gf had her lock cut off it
was chained to the entrance railings outside Chiswick Town Hall , the Tw—st will get them if they want ,
There is a big push in London for alternative commuting , they are going to spend millions apparently on cycle lanes etc , security is seemingly not high on the list for those in a similar situation to your Lad ,