uncle,
I have heard that it was the CAA who had the restriction, and also that it was probably the reason that Alan Bristow got the 212's when he did.
I heard too that he was granted permission to fly singles over built up areas (Whirlwinds??) during some floods just before he got the 212's.
This info is second hand at best so it may well be wrong, don't quote me.
UL