Police are warning people not to leave valuables in their cars as they play sport after dark.
Thieves have targeted car parks where people play sport after work - so they can steal without being seen.
At a meeting of Little Gaddesden Parish Council, PC Stuart Francis said: “We do not want to see an increase in theft from parked vehicles during sporting events.
“But this may happen now as it’s coming towards Christmas. We have had a few in Hemel Hempstead during football matches.”
Police are sending letters to the drivers of parked cars where they find valuables left on display.