The Hatton Garden burglars made a failed attempt to drill into a safe at a Bond Street jewellers ahead of their notorious heist, a court has heard.
Video of the attempted operation at high-end store Chatila, from the August bank holiday in 2010, was shown to Woolwich Crown Court.
The final heist suspect Michael Seed, 58, is standing trial over allegations he was an alarm expert nicknamed "Basil" who played a key role in both heists.
Detective Sergeant Jamie Day told the court how a Chubb Sovereign safe in Chatila was targeted with a drill after the store's alarm systems were tampered with.
Burglars gained access through the lift shaft, the trial has said.
A milky white liquid was seen on some of the items stolen and the empty display cabinets and court earlier heard how a similar fluid was found on safe deposit boxes at 88-90 Hatton Garden, the court heard.
Images showed holes in the walls surrounding the large metal unit as well as in its door and mechanisms.
An electronic timer system appeared to have had its casing removed.
"Drilling had taken place in the tumblers on the door," said Det Sgt Day.
"Holes were made into the plasterboard around the safe.
"The actual door of the safe itself had been drilled."
Det Sgt Day told jurors the safe was "not breached" however the court heard the thieves instead made off with £1 million worth of jewellery and watches from the store's display cabinets.
In the Hatton Garden heist an estimated £13.7 million of gold, cash and gems was looted after a hole was drilled through the vault wall over the 2015 Easter bank holiday weekend.
The probe into the heist revealed some of the same men had committed a "strikingly similar" burglary on the late August Bank Holiday weekend in 2010 of the Chatila jewellery store in Bond Street, the court has heard.
Five men, Brian Reader, 79, John "Kenny" Collins, 78, Daniel Jones, 63, Carl Wood, 61, and Terry Perkins, who died aged 69 last year, have been convicted of conspiring to carry out the burglary.
Seed is alleged to have taken part in the raid with Jones, who pleaded guilty to the burglary, as well as Perkins, who died in prison last year.
Police raided Seed's one-bedroom council flat in Liverpool Road, Islington, on March 27 last year, the court was told.
It was three years after the heist in London's diamond district, just over two miles away from the property.
Seed denies two charges of conspiracy to commit burglary and one charge of conspiracy to convert or transfer criminal property.
