by Chris Allen

A thief who stole a charity collection tin from a Christmas lights display left an expensive mountain bike behind in his haste to escape.

The bike is thought to be worth £900, if bought new. The teenager and his accomplice got away with just £40 in donations.

Every year, builders Lee Brailsford, 31, and his brother Paul, 28, decorate their mother's Brentry home with a festive lights display to raise cash for charity.

Any money raised this year will go to the Bristol Children's Hospital Wallace and Gromit's Grand Appeal. Last year, they raised more than £1,600.

And despite the sharp downturn in the economy, the family decided to carry on with the fundraiser this year so as not to disappoint anyone.

It costs about £100 a week to run the lights, from 5pm to 10pm every evening.

The teenage thieves, thought to be about 15 years old, raided the cash tin on Sunday evening at about 10pm – just before the lights were turned off.

Lee, who lives just around the corner, said: "We normally turn the lights off at about 10pm each night and empty the collection tin.

"They tried to rip away the collection box but couldn't get it so just helped themselves to the money. They were seen doing it and we chased after them. When we challenged them, one of them dropped his bike and ran off.

"The police now have the bike, a Carrera XC, which we've seen for sale in Halfords for £899."

He added: "We empty the collection tin every night and have now secured it so it can't be tampered with.

"They would have only got away with about £40.

"We're trying to keep it all going through all the gloom and doom of the credit crunch and raise some money for sick children – but as usual there's some who are trying to ruin it for others."

The Brailsford brothers, who claim to have Bristol's biggest domestic Christmas lights display, have decorated their mum's home for the past 12 years. For the last five years, they have raised money for charity.

The display has got bigger each year and now covers the house and garden of the corner house in Trevisa Grove, Brentry.

Martin Dunscombe, an Avon and Somerset police spokesman, said: "We are investigating the incident."