Come to Leicestershire and you'll find the answer in one town - Coalville. The story goes there was a murder there some years ago. The police concluded that the murderer was local and set about DNA testing the townspeople to find a link to some found on the victim.
They found a match and discovered that the murderer was ... well, could have been anyone in Coalville, really.
By the way, Coalville folk will tell you that the inbreds all live down the road in Hugglescote. Believe what you will. ;-)