I think in a lot of places police are allowed to drive classes of vehicle they aren’t licensed for in an emergency, and the force’s insurance covers them at least under some circumstances- usually to let them move abandoned vehicles out of the way of traffic.
For instance, I have a friend who uses a wheelchair and drives a modified van with hand controls that she gets into via a ramp at the back. A couple of years ago, somebody parked (inconsiderately and illegally) behind her- a passing policeman offered to get into the van via the side door and drive it forwards so she could get in. AFAIK you are only allowed to drive that sort of modified vehicle, where the normal controls have been replaced, if you passed your driving test in one.
(Of course, being unfamiliar with the controls, he then proceeded to damage them- but it’s the thought that counts…)
