Scotland Yard has revealed it is investigating why the force did not respond to an intruder alarm activated during the Hatton Garden jewel heist.

The probe will look into why a call from an alarm firm was given a grade that "meant that no police response was deemed to be required".

The Central Communications Command of the Metropolitan Police received a call at 12:21am on Good Friday, stating an alarm had gone off at Hatton Garden Safety Deposit Company.

Scotland Yard said in a statement: "The Metropolitan Police Service (MPS) has been making initial inquiries into what calls were received relating to the Hatton Garden burglary last weekend."

"The (12.21am) call stated that a confirmed intruder alarm had been activated at the Hatton Garden Safe Deposit Ltd."

"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."

"It is too early to say if the handling of the call would have had an impact on the outcome of the incident."

It comes after potential victims voice anger at the police's failure to provide them with information about the investigation.

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 up to 70 safety deposit boxes.