A gang of robbers have stolen jewellery worth tens of thousands of pounds from two stores inside west London's Westfield shopping centre.
A group of about 10 men wearing balaclavas used sledgehammers to break a fire door to get into the centre at about 0120 BST.
The thieves then targeted branches of De Beers and Tiffany & Co.
The gang escaped in three cars, one of which was followed by police, before officers lost sight of it.
No arrests have been made and no injuries were reported.
Private security
Officials at Westfield, which opened in October 2008 and houses more than 250 shops, said it was the first burglary of its kind to take place at the centre.
A spokeswoman for the shopping centre said: "Westfield is working closely with the Metropolitan Police to identify suspects and recover property.
"No-one was injured during the incident, which took place whilst the shopping centre was closed, and our on site security staff responded immediately as did the local police".
The Westfield shopping complex pays for its own private security staff and police teams under an agreement with Hammersmith and Fulham Council.
BBC News
