Police in Market Harborough have warned about a spate of thefts from cars in villages to the north of the town.
The 42 thefts since the beginning of the month were around Fleckney, Kibworth, Bushby, Thurnby and Scraptoft. Most of the cars had not been locked by their owners.
Pc Steve Winn, based in the town, has issued a “Lock It Or Lose It” warning to village householders.
He said: “Myself and four colleagues have been round the villages ourselves trying car doors, dressed in plain clothes.
“We found 30 parked cars unlocked in one day, and were only challenged once by locals. I was genuinely surprised.”
He urged people to lock their cars at all times and not make it easy for thieves.