Seven men are being questioned after police foiled what they believe would have been Britain's biggest robbery.
One man is still on the run
The target was £40m of gold bullion and between £30 to £40m in cash, stored at the Swissport Cargo Warehouse at Heathrow Airport.
Armed police lay in wait for the gang as a van smashed into warehouse doors. More than 100 officers were involved.
One man is still on the run. The arrested men are being questioned at west London police stations.
The gang threatened staff with at least one firearm, knives, cudgels, hockey sticks and lumps of wood, after reversing at speed through the warehouse shutters on Monday morning, police said.
They rammed their way into the warehouse on the outskirts Heathrow having apparently got in by producing what appeared to be legitimate paperwork.
They forced their way into a secure area containing a large quantity of precious metal and bank notes.
But as the men tried to escape, officers fired special bullets - designed to deflate tyres with minimal damage - into the van's wheels.
Six men were arrested but two suspects fled in a hijacked white van.
The driver of the van gave himself up near the airport shortly before 1300 BST.
But the other man escaped on foot.
The hijacked van was recovered, and those arrested taken to West London police stations for questioning, the Metropolitan Police said in a statement.
A white van smashed into warehouse doors
One officer had suffered minor injuries, the statement added.
A Swissport spokesman said security guards had stopped the van at the complex's main entrance - but the gang had had legitimate paperwork to collect a shipment.
The gold bullion and cash had arrived earlier on Monday, he added.
"Some members of higher management were aware this raid was going to take place - but for operational reasons this information was not shared with the rest of the workforce," the spokesman added.
"This has obviously been a very shocking experience for many of our members of staff - some are very upset, and counselling has been arranged for them.
"The company was pleased to co-operate with the police, and congratulate them on the outcome."
FOILED HEIST AT HEATHROW
1 1000 BST: Armed gang ram warehouse shutters in a van and threaten staff. They are trying to steal £40m in gold bullion plus cash.
2 Police lying in wait disable the van and arrest six of the gang
3 Two men hijack another van and drive off towards Stanwell
4 1300 BST: Seventh man is arrested
The gang is thought to have had inside information about the warehouse.
Detective Superintendent Barry Phillips, of the Flying Squad, said: "They knew where the gold bullion was located inside the premises
and went straight for it."
But the area had been under surveillance for weeks.
Swissport's management had been "very co-operative", Det Supt Phillips added.
"In preventing this attack, we have foiled what would have been one of the biggest robberies ever committed in the UK. We believe that these men were part of an organised criminal enterprise," he said.
"A lot of planning and preparation went
into the attack - but the Flying Squad was one step
ahead of the team for some time."
The swoop operation, codenamed Cartwright, was part of the larger Operation Grafton, an initiative launched by the Met's Specialist Crime Directorate in partnership with Thames Valley Police, Surrey Police, HM Customs and Excise.
Det Supt Phillips said the initiative had enjoyed "substantial success in dismantling the organised networks that have been operating in and around the airport" in the past year.
World's biggest robberies
Apr 1945: Reichsbank in Berlin, Germany looted. Estimated £2.5bn stolen.
Feb 2003: £65m diamond robbery in Antwerp, Belgium
Jul 1987: £60m robbery at Knightsbridge safety deposit centre, London
1994: £29m gems raid in Cannes, France
Nov 1983: £26m Brinks Mat robbery at Heathrow, London
Jan 1976: £22m robbery at British Bank of the Middle East in Beirut, Lebanon
Source: Guinness World Records
It was "a classic example of that partnership approach" and had "removed a serious and organised criminal gang", he added.
The gang were "career
criminals", with some known to police, Det Supt Phillips said.
The Met's Specialist Crime Directorate head Assistant Commissioner Tarique Ghaffur said: "A professional
team of armed robbers have now been removed from society."
Airport operator BAA Heathrow said in a statement: "We are delighted.
"We have worked very closely with the police and cargo operators at Heathrow in recent months on improving security around valuable cargo."
Swissport, majority-owned by London-based private equity house Candover Partners Ltd, handles more than three million tonnes of cargo every year.
Its UK customers include British Airways, First Choice, Ryanair, Monarch, Britannia, Thomas Cook Airlines, easyJet, FlyBe, Eastern Airways and Virgin Atlantic.