A bogus detective who tried to con a man into handing over £7,000 was foiled when genuine police intervened.

A man claiming to be with the Metropolitan Police called the victim yesterday to tell him his bank account had been infiltrated and cash was needed for forensic tests.

The scam has been replicated across Essex and Suffolk, with one victim in Dedham having £2,500 withdrawn from his account when he handed over cards before they were stopped.

The victim, in his 80s, took a bus from his home to Brentwood to carry out the instruction, but his worried wife called her daughter for advice.

Her daughter was aware of the scam and called 999.

Sgt Terry Fisher from Essex Police who was on patrol in the town rushed to the High Street bank on an emergency response, arriving eight minutes after the 999 call.

He got there just as the victim was walking out with a large packet containing the cash.

Sgt Fisher explained the caller had been a fraudster, queued with the victim until the money was paid back into the bank, then gave him a lift home.

The daughter told Essex Police she was “extremely grateful” for their efforts.

In a similar incident also in the town on Monday a woman handed over £4,800 to a courier after a call from a man posing as a detective chief inspector in the Met Police.

Det Ch Insp Paul Maleary from Essex Police said: “These two incidents show how ruthless,cunning and convincing these tricksters are. They are the lowest of the low.

“In the first incident the man’s daughter realised immediately what was wrong and dialled 999 immediately. Eight minutes later her father was being helped by Sgt Fisher and the money was safely returned to the bank account.

“It was excellent work by Sgt Fisher and the controller who took the call at the Essex Police control room.

“This case is a graphic example of how family members need to look after elderly relatives and ensure that they are aware of these scams.

“Sadly in the second case the victim was tricked and the scam was not reported to police until about six hours later.

“We have been making inroads into the organised crime gangs carry out these crimes and numerous arrests have been made. At a recent trial a man was jailed for five years for his part in a case at Buckhurst Hill.”

People are being reminded that police would never ask for bank account details or a PIN, ask you to withdraw money and send it to them, or bank cards.

More than 800 similar thefts and attempted thefts have been reported in Essex since the scam first came to light in January 2013, with more than 140 people tricked out of money.

The total stolen is more than £450,000.