This implies the ISP outfit actually had the proper security procedures in place to be able to at least contain the police for a bit. And the onsite security were actually worth something.
I used to regularly go to an unnamed datacentre near London. For non-ex-army environment the place was really tough to get into.
You need to get through a full-sized steel turnstile controlled by the security booth, then enter the security boot through steel door, mini-turnstile, another steel door. This only gets you into the courtyard, not the actual building. There are still something like 3-4 locked doors until you can reach equipment. And oh, another full-sized turnstile for every data area, transparent walls but still.
Vehicles were only allowed in if they were pre-registered, twin gates, metre high retractable bollards between the gates, likely able to flip over a lorry.
The security are ex-Gurkha. Look small and puny, but I suspect they can carry me for 1/2 mile, and I'm well over 6'. I would certainly will not spill their pint, or if I do will ask with my sweetest voice if they wanted replacement.
Biting the hand that feeds IT
