A British court has reportedly jailed an obsessive car thief who carefully cleaned the vehicles he stole, before returning them to their owners in perfect condition.

The Daily Telegraph reports that Colin Sadd, described by one judge as "the man you would most want to steal your car", received a six-year sentence at a court in Sheffield, northern England.

The 41-year-old contract cleaner, who has 155 previous convictions for mainly car-related crimes, admitted five counts of stealing cars and asked for 31 others to be taken into consideration.

The court was told that Sadd would dress smartly and pose as a customer at vehicle showrooms before snatching keys and driving away in a car.

After driving them for several hours, he would wash and polish the car, as well as thoroughly cleaning the exterior, before returning them undamaged to their owners, the paper said.