Police hunting a gang that robbed two jewellery shops in central London have released CCTV images of the raiders.
The gang struck at De Beers and Omega stores in the Royal Exchange shopping centre in the City of London at about 2200 BST on Saturday.
Jewels worth an estimated £380,000 were stolen by the robbers, who fled in a red BMW.
The newly-released images show balaclava-clad robbers using hammers to break cases of jewels.
A City of London Police spokeswoman said: "The force is treating this incident very seriously.
"A team of dedicated detectives is currently involved in the investigation and is liaising with other police forces."
The four thieves are believed to have broken through a padlocked gate then smashed the shop windows with sledgehammer.
The thieves, wearing hooded tops and balaclavas, took diamond jewellery and watches from the window displays.
There have been no arrests.
On Monday former Flying Squad officer John O'Connor suggested the raiders may have had inside assistance.
He said: "The villains did not drive up on the off-chance they could get through security gates.
"There is always the suspicion that they had somebody on the inside."