The heist – in which thieves made off with the contents of around 70 safety deposit boxes – was not picked up by officers until Tuesday morning - five days later - when staff returned after the long bank holiday weekend.
But there has been speculation that an alarm would have triggered a call to the police. This afternoon it was confirmed that a call was received by the MPS Central Communications Command just after midnight on Friday.
The call stated that a confirmed intruder alarm had been activated at the Hatton Garden Safe Deposit Ltd, the target of the heist.
“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,” a police statement said today.
“We are now investigating why this grade was applied to the call. This investigation is being carried out locally.”
The statement added: “It is too early to say if the handling of the call would have had an impact on the outcome of the incident.”
Yesterday it emerged that the thieves did not force entry to the building but used a heavy duty Hiti Hilti DD350 to bore holes into the vault once inside.