Two men sprayed a nine-year-old boy with noxious chemicals during a robbery.
The men attacked the young boy and two other women after they entered the house in Brent Street, Brent to buy two laptops that had been advertised on Gumtree.
As they were looking at the products, one of the men sprayed the women, aged 28 and 26, with what police described as a "noxious substance".
The nine-year-old attempted to run away but tripped and was also sprayed by the men who fled the scene with the laptops.
Paramedics treated the three victims at the scene but none required hospital treatment.
One of the victims managed to record footage of the suspects on their mobile phone during the incident on Wednesday 2nd March at 3.50pm.
The suspects are:
one was wearing a dark coloured leather jacket and had short brown hair
the second was wearing a black jacket and had a tattoo on his neck
Police have urged anyone with information to contact police via 101 - quoting reference numbers 205697 and 205700 - or Crimestoppers anonymously on 0800 555 111.