I was driving around the UK recently, and had a British friend ride along with me to critique my left-side driving skills. We were on a "Carriageway" (so cute) and I came alongside a British Patrol car- a BMW wagon minus the car seats in the back but with Bright Yellow and Orange stickers. It was going about 5 miles under the speed limit, but because I was out of my comfort zone, I slowed down, unsure whether I was speeding or not.

The Friendly UK Police

My friend told me to go ahead and pass him. Evidently, British patrol cars in England drive deliberately under the speed limit so that traffic can freely overtake them without fear or worry of being cited for speeding. Not the case here in the States, as I can attest both as a civilian driver, and the owner of two Ford Crown Victorias (one a genuine Police Interceptor).