Thieves raided a jewellers shop but were thwarted when an onlooker took the keys from their getaway car.

Four men used sledgehammers to smash their way into the WE Clark and Son shop in Cliffe High Street, Lewes, at 3.30pm yesterday.

Dressed in green boiler suits and balaclavas, the men bagged tens of thousands of pounds worth of stock in front of two terrified staff and four customers, none of whom were injured.

But last night three men were being questioned on suspicion of being members of the violent gang responsible for the attack on the store.

The thieves had been plundering the shop for luxury jewellery when people in the crowded street outside hatched their own plan.

A woman parked her car across the narrow road, blocking in the raiders' red Peugeot getaway car.

One man put traffic cones and a roadworks sign in front of the vehicle and another took decisive action and grabbed the keys left in the car's ignition.

When the thieves got outside, they saw what had happened and fled down the street on foot - chased by three onlookers who had seen them leave the shop.

The raiders then jumped into another car, possibly left as a back-up getaway by the nearby Cuilfail tunnel. Three people were later arrested after police stopped a car on the A22 near the Boship roundabout at Hailsham.

David Clark, the managing director of the jewellery shop, commended his staff and the customers in the shop for their bravery during the three minutes or so the men were inside. He said: "My staff took every professional step to ensure the safety of the customers which was paramount."

One onlooker who chased after the four men as they ran away from the shop was James Pullan from Fletching.

He saw the getaway car pull up outside the shop and the four men get out.

He said: "I saw them smash their way into the shop with sledge hammers and I knew this was a serious raid."

Yesterday's raid came four months after a similar raid saw £250,000 of luxury watches at a heist at an Eastbourne jewellers.

In that raid, three men in paper boiler suits and balaclavas smashed the windows of W Bruford in Cornfield Road with sledgehammers.

Their haul included 60 watches made by leading brands.

Sussex Police have appealed for witnesses or anyone with information about yesterday's raid to call Detective Chief Inspector Mark Ling on 0845 6070999, quoting serial 1129 of May 8.