Counter-terrorism police investigating the death of ex-MP Ann Widdecombe have reopened an inquiry into a report of an attempted burglary at a London address in April last year.
No arrests were made at the time and the investigation was closed.
On Friday Counter Terrorism Policing said a line of inquiry had been identified that was not "pursued by them at the time".
It has made a mandatory referral over its handling of the initial investigation to the Independent Office for Police Conduct (IOPC).
The Metropolitan Police had received a report of an attempted burglary in the Greater London area, the statement said, with the initial investigation carried out by the Metropolitan Police and Counter Terrorism Policing London.
The police watchdog has said it is investigating allegations that a Counter Terrorism Policing London staff member "failed to identify and pursue a line of inquiry" related to the attempted burglary.
"Counter Terrorism Policing London has been notified of our decision, and no further information is available at this early stage."
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