A shopper was tricked into paying £700 for a bottle of mineral water by two conmen who convinced him he was buying a cheap laptop computer.

Police believe the incident is the latest in a series of similar scams on at least ten people.

The embarrassing sting took place in Sainsbury's car park at Lyon's Farm, Worthing.

The 29-year-old victim from Worthing told detectives he was about to go shopping when a grey car pulled up near him and a man offered him a chance to buy a laptop computer, which said he had in his car.

He was particularly persistent and the victim relented and went to a cashpoint to withdraw £700.

He got into the car to make the exchange but he realised the bag contained only bottled water.

An argument ensued and the victim fled after he was threatened with what he thought was a knife.

The conman who approached him in the car park was about 25 to 35 years old, had an Irish accent, light brown hair, was of medium build and wore a dark jacket.

The driver was blond and in his 20s.

Police said ten similar robberies had happened in the last 18 months in Worthing, Lancing, Shoreham, Rustington, three in Brighton and three in Hove.

Detective Sergeant Ray Scales: "There has been a series of these robberies, all substituting the computer for water. People should always be wary of buying from strangers."

Anybody with information should contact the police on 0845 6070999.