Jewel Heist: How Easy Was Vault Break-In?

Drilling experts have demonstrated on Sky News how burglars would have broken through a two-metre-thick wall in a lucrative raid at the heart of London's diamond centre.

They said those behind the heist would have had to use specialist power tools costing thousands of pounds to get through reinforced concrete walls in the basement of the building in Hatton Garden.

But that is a tiny fraction of what the burglars are expected to make from breaking into as many as 70 boxes inside Hatton Garden Safe Deposit Ltd.

Video of an expert using a similar drill on a large block of concrete shows just how big the scale of the operation was - after a minute, it had hardly scratched the surface.

Joel Vinsant, secretary of the Drilling and Sawing Association, told Sky News: "It would take anything from 45 minutes to an hour-and-a-half - it's two metres thick so they'd need specialist equipment."

The thieves would also have needed a constant water supply to keep the drill cool as it powered through the thick wall, he said.

"They'd have a lot to set up in terms of getting it under way," he said.

The thieves are thought to have accessed the building on upper floors. Police believe they disabled a lift and climbed down the shaft into the basement, but there was no sign of forced entry anywhere in the building, which the safe deposit company is only part of.

Officers found a scene of chaos when the theft was discovered on Tuesday, with dust, debris and power tools strewn across the floor.

On Thursday, they said only a few people would have the skills to carry out the "sophisticated" operation over the Easter weekend.

Former Flying Squad member John O'Connor has suggested the criminals would have needed help from someone with inside knowledge.

Victims are still being identified, but they are likely to have been left millions of pounds out of pocket.

Sky's Crime Correspondent Martin Brunt said one jeweller had told him that five of his customers were victims - one had lost emeralds, diamonds and other valuables to the tune of £1m.

He said: "Other customers have told us that they use this safe deposit centre to avoid big insurance premiums, so some of the stuff here won't have been insured.

"A little while ago somebody came and stuck two letters on the sign here in front of the word 'Safe' so it read 'Unsafe' - it was there for a few minutes and reflected a pretty sombre and angry mood here."