A lot of the X civil service org have some odd grandfathered powers BT's an d the royal mail internal security have more powers the average function in an ordinary PLC has.

Not Bruce Sheniers resignation statement and notice how careful he is to be nice to BT security.

everyone in the UK has powers of arrest afaik - you don't even need to be a citizen.

however, i'd imagine that these guys are instructed on how to use it, unlike the wider populace