Unmarked Police on M25 - meldrew
Unmarked possibly but not unnoticeable. I am not a regular on the M25
but saw a driver pulled in by a bright orange RS Focus last week clockwise just North of Wisley/A3.
Beware!

A few days earlier I had been travelling South on the M40 in very light traffic and saw a fast approaching Golf in my mirror. It moved out well before overtaking me and carried on in the empty overtaking lane at great speed.
I turned to my wife and said it was actually quite nice to see somebody driving both quickly and competently. I had hardly finished my sentance when the slipstream of the fully marked police car nearly blew me onto the hard shoulder!

Doing a bit of arithmetic, if the Golf was doing, say, 100mph and a half mile start I wondered how fast the police car was going to pull him in within the next mile. By the time we caught up the policeman was out of his car looking fairly well armed and menacing. I'm sure it was "only" a speeding offence but I felt quite sorry for the driver.......
Unmarked Police on M25 - ifithelps
A bright orange Focus?

To some VAG drivers, that's almost entrapment. :)
Unmarked Police on M25 - dave993

Also runs up and down the M3. M25 to sunbury cross

Unmarked Police on M25 - Altea Ego

and the A3. Think its based at the police garage at Chertsey, seen it knocking around there a bit.

Unmarked Police on M25 - piston power

How fast are the police allowed to drive is there a limit?

But yes no problems with unmarked cars you can hardly advertise here we are so we all slow down can you.?

Im sure most get away with 80 even 90 mph it's when over that and driving like an idiot is when they get pulled.

Unmarked Police on M25 - retgwte

it varys up and down the country, but typically police advanced drivers have permission to disregard 70 limits, other police drivers do not - so usually dog vans and so on should not be breaking the limit

30 limits they are supposed to stick to unless on a job, other limits have verying rules

but they dont have permission to drive with one inch braking distance from the vehicle in front as the police bikes on the A3 do regularly (for instance) - been meaning to get some film of them doing this

and so on and so on