Elderly people are being warned of a snowballing scam epidemic with at least 29 reports in the last three weeks.
Police managed to all but eradicate the so-called 'bank courier scam' in Sutton several years ago - but it has come back with a vengeance with a surge in reports in the last three weeks.
The scam works by a person targeting an elderly person and phoning them purporting to be their bank to tell them there is a problem with their bank card.
The victim will be encouraged to input their PIN using the phone then the caller will sell them a courier will be visiting to pick up their card.
Usually an innocent taxi is used to unknowingly pick up the victim's card and deliver it to the criminal.
Sutton police Detective Inspector Sarah Rees said: "We had a spate 18 months to two years ago and we managed to reduce it. But now it seems that it's started again.
"It's just heart-breaking to see it happen - the oldest victim in the recent spate is 89-years-old.
"The perpetrators are cruel and heartless individuals who set out to trick and confuse people who are elderly and vulnerable.
"We want residents to talk to their elderly neighbours and make them aware of this scam so they don't get tricked out of their money."
There are variations on the scam including one that was used to trick a 75-year-old Belmont woman out of £2,940 last week.
A caller phoned to say her account had been used to fraudulently buy two computers and she should call police.
The woman hung up the phone but the caller did not so when she picked up the phone to redial she was still connected to the original caller.
The victim gave the caller her details thinking she was talking to a police officer. A courier picked up her card later that day.
The scammers continued to target the woman and the following day she received a further call from someone claiming to be a police officer.
She was asked to with draw £4,000 from her bank because her bank was being investigated for handing out counterfeit notes. She was told not to speak to her bank as it may be involved in the alleged fraud.
The woman withdrew £2,500 that was again picked up by a supposed courier.
Police have urged people never to give their PINs out on the phone - banks will never ask for this - and if anyone asks for your bank details in an unsolicited call to hang up and use a different line or wait five minutes for the line to clear to call police on 101.
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