SHOPPERS were treated to a supermarket sweep at a packed store when a thunderstorm knocked out all the tills.

Managers at the Asda supermarket, at Monks Cross, York, told delighted customers to pay what they wanted for their goods.

The store was soon packed as word spread throughout the city and the gesture sparked a shopping bonanza.

Every till at the store was off for two-and-a-half hours becasuse of a fault in the computer system, caused by the electrical storm.

Rather than let frozen foods melt in trolleys as staff and customers waited for the power to come back on, check-out assistants asked shoppers how much they thought was in their trolley or basket and how much they would usually spend on food.

Customers got on their mobile phones to tell friends and relatives about the incident and to get into the store.

One shopper said he paid only £30 for a full week's shopping.

He said: "It was great. We guessed we had about £40 of stuff in there and they just said to give them £30.

"I don't think anyone was complaining."

Store manager Colin Storey said about 15 tills were down between 9pm and 11.30pm. New customers were allowed through the doors even after word had got around the city.

"Customers were on their mobile phones telling their friends and family to get down to Asda," said Mr Storey.

"We advertise as being open 24 hours and just because we have got computer problems it does not mean customers should not be able to do their shopping as normal.

"It was worth it to keep things moving and to keep our customers happy."

Mr Storey said any financial loss would have been minimal.