People are being urged to be on the lookout for bogus builders preying on vulnerable people.

Police in Harrow are currently investigating two incidents in different parts of the borough in which fraudsters duped elderly people into handing over large sums of money.

The first case involved a woman who was approached by a man while she was shopping in an Edgware supermarket, asking if she wanted her windows cleaned.

She told him she did not and walked away, but when she arrived home the man from the supermarket knocked at the door with another man offering to clean the windows for £15.

The woman agreed and let them into the house. Once inside the men climbed into the loft space and told the victim there was water damage to the roof, claiming and they could fix it for £4,000.

Taking the men at their word the woman went to the bank to withdraw the money and gave it to the men who said they would be back the next day.

The fraudsters never returned to the address told the victim over the phone that they were having trouble with their van.

The woman described one the of the men to the police as white, 35 to 45 years old, of large build, with dark brown hair, with an English accent and wearing a white vest.

Detectives are also investigating a similar incident in which a man pretending to be a builder called at the home of an elderly man in Harrow after approaching him as he was out shopping.

The bogus builder told the victim he needed work done to his roof and it would cost £3,000, which the elderly man handed over.

Police say the man is described as white, around 25 years old and approximately 5ft 8ins tall.

Detective Constable Sue Georgiou of Harrow Police said: "This is a despicable crime, particularly because these criminals prey on the most vulnerable people in our society. “

In both cases we believe the suspects followed the victims home after approaching them when they were out shopping.

“We are asking members of the public to be vigilant, not to let random callers into their homes and not to hand over any amount of cash.

“Ask them to call back when a family member, friend or neighbour is there. If the caller is genuine, they won't mind this. If a caller is persistent, call the police."