The Metropolitan Police has come under fire after it emerged officers initially failed to go to the scene of the Hatton Garden jewel heist despite a burglar alarm going off.
A security firm had contacted the force about an intruder alert at the safe deposit company shortly after midnight on Good Friday.
But the call was graded in a way that meant officers did not consider it worthy of a response.
And it was not until Tuesday morning, following the four-day bank holiday Easter weekend, that the raid - one of Britain's biggest - was discovered.
The Met is now investigating why the force did not respond to the alarm activated as the heist was thought to be getting under way.
Police insisted it was too early to say if the handling of the call about the alert would have had an impact on the outcome.
But the revelations have led to anger from potential victims who spoke of their shock that the police "just weren't there".
Millions of pounds worth of gems were thought to have been stolen in the raid in London's jewellery district.
Michael Miller, from Knightsbridge, who may have lost £50,000 in uninsured jewellery, said: "I am just so shocked and disappointed to hear the police didn't answer that alarm.
"I mean before, we thought maybe the police didn't even know about that but now we know that they knew something was wrong.
"This completely changes things, the knowledge that something could have been done.
"The police pride themselves on being somewhere in a couple of minutes, but on this occasion they just weren't there."
A store owner near the scene, who did not wish to be named, said: "It's just shocking that someone didn't answer that call that come in when the alarm went off.
"You think what on earth isn't a high priority call if it's isn't a safe deposit alarm going off in there.
"I know they're investigating but really what is the good of that when the damage is done. There are people who will have lost their livelihoods because of this."
Scotland Yard said: "The call was recorded and transferred to the police's CAD (computer aided despatch) system. A grade was applied to the call that meant that no police response was deemed to be required.
"We are now investigating why this grade was applied to the call. This investigation is being carried out locally."
Those behind the raid disabled a communal lift shaft and climbed down to the basement before using power tools to drill through a two-metre wall into the vault.
Once inside, they ransacked a total of 72 safety deposit boxes, although five were empty at the time.
A further 11 were due to be "drilled out" due to non-payment of fees, meaning detectives are attempting to contact a total of 56 box holders.
