Elderly residents are being warned about a phone scam after it emerged that 48 people have been targeted in Waltham Forest this year.
Conmen posing as police officers or bank officials have been telephoning vulnerable people and telling them they have been the victim of fraud.
A courier is then sent to homes to collect bank cards, which are then used to steal money.
Superintendent Chris Nelson has asked families warn elderly relatives to protect themselves.
He said: "Thieves like these prey on the most vulnerable members of our community.
"The effects of becoming a victim of crime run far deeper than a loss of property, but for vulnerable and elderly victims the effects can be lasting and have a devastating influence on their quality of life.
“My officers will never ask for bank details and we do not send couriers to collect evidence."