Detectives are appealing for three white men in black puffer jackets following an aggravated burglary at a home in Chiswick.
Police in Hounslow want to trace the tricksters who knocked on a door in Compton Crescent and posed as workmen before pushing their way in.
The incident happened on September 25 at about 12.50pm.
The victim opened her front door and saw two men who said they were from the water company and had to check a leak in the kitchen.
They pushed the victim out of the way and walked into the kitchen and started checking the sink.
The victim followed them in when she heard her son shouting from upstairs, where a third male was spotted and punched the son before running downstairs.
On hearing the noise both suspects downstairs ran out of the house, followed by another man, and were seen going towards Falconberg Road before they drove off in a black BMW.
Police believe suspect number three gained access to the house and walked upstairs carrying a file and started checking the bedrooms before he was confronted by the victim's son.
The injured son did not require any medical attention.
Suspect one is described as white, about 20-years-old, of large build and was wearing a black puffer jacket and jeans.
The second suspect is described as white, about 20-years-old of thin build and was wearing a black jacket and had brown hair.
Suspect three is described as white of stocky build and was wearing a black puffer jacket with a hood over his head.
All three spoke with an English accent.
Detective Constable Emma Pestridge said: “These men are blatantly tricking their way into the homes of unsuspected homeowners posing as legitimate workmen when they are clearly not.
“We serve this as a reminder to homeowners to make the relevant checks and ensure those workers are genuine before they enter your home.
"If in doubt always contact the police."
Anyone with any information is asked to contact DC Emma Pestridge on 0208 247 6650 or call Crimestoppers Anonymously on 0800 555 111.
