Cambridgeshire Police are reminding people to remain vigilant when answering the door to or receiving calls from people claiming to be from the Metropolitan Police.
Instances of people impersonating Metropolitan Police officers have been reported in the county and polie are reminding residents to ask for ID.
A spokesman said: “If you have doubts about someone phoning you, hang up, ensure the line has been terminated and ring back on an official number.
“Don’t be afraid to ask for identification in person and call 101 to verify their identity.
“Please pass this message to elderly friends, neighbours and relatives.”