British police said they had arrested seven suspects, including three pensioners, on Tuesday over a multi-million pound raid in London's jewellery business district last month, which local media say could have been the country's biggest-ever heist.

In the audacious raid, thieves abseiled down a lift shaft at Hatton Garden Safety Deposit Ltd over the Easter weekend when businesses in the area were closed, and bored their way through a two-metre thick wall into a vault using a heavy duty drill.

There, they ransacked dozens of boxes, taking cash and gems, some of which belonged to businesses in Hatton Garden, which is home to almost 300 diamond, gold and gem dealers and more than 50 jewellery shops.

Police have given no official detail of what was stolen but media have estimated it could be as much as 200 million pounds ($300 million), dwarfing the amounts taken in Britain's previous biggest heists.

On Tuesday, more than 200 officers raided 12 addresses in north London and southeast England on Tuesday, arresting seven men, all British and aged over 48, on suspicion of conspiracy to burgle. Three of the men were aged 67, 74 and 76.

Detectives said large bags containing "significant amounts of high value property" were found in one of the properties they raided which they believed had been stolen during the burglary.

"This has been an exceptional, complex investigation and I thank everyone for remaining patient," Detective Superintendent Craig Turner, head of London Police's Flying Squad, told reporters.

Police have faced criticism for failing to respond to an alarm at the safe depository that went off during the burglary, and Commander Peter Spindler admitted that proper procedures had not been followed.

"For that I want to apologise," he said, although he added that there had been no external sign of a break-in.

"At times we have been portrayed as if we've acted like Keystone Cops," Spindler said. "But I want to reassure you that in the finest traditions of Scotland Yard these detectives have done their utmost to bring justice for the victims of this callous crime."

Britain's record heist was carried out at a Securitas cash depot in Tonbridge, southeast of London, in 2006 when robbers stole almost 53 million pounds in cash.

In 2000, police foiled a daring attempt to steal 350 million pounds worth of diamonds from a display at London's Millennium Dome in what would have been the world's biggest-ever robbery.-Reuters