A teenager is warning others to be cautious after she was robbed at knifepoint as she sold her phone in Harlesden.

Lourassa Campbell was selling her Apple iPhone 7 for £280 after meeting the buyer through car boot sale app Shpock.

She was with the young man in Chadwick Road on January 7 when both were robbed by another man passing on a bicycle. The 18-year-old, from Harlesden, had agreed to meet the 17-year-old boy to hand over the phone for cash when they were targeted. She said: “The boy said there was an estate near Roundwood Park and told me to meet him there the next day. He was late so I called him on my iPhone X.

“I handed him the iPhone 7 and he took out the first £100 from his jacket and gave it to me.

“As he was counting out the rest a boy came up on his bike, took the money out of his hand and came up to me and pushed me over. He had a knife in one hand and with the other he took the iphone X I had out of my hand and the money and stomped on me.”

She said passersby were alerted to her screams and called the police, adding: “The police took both our statements. Afterwards the policeman told me it could have been a stitch up. The guy on the bike took both the phones and all the money like he knew we’d be there.

“I don’t have a problem with the app, it’s a legitimate business but I just want people to be careful.”

Police confirmed they are investigating whether the robbery was a set up and no arrests had been made. They are seeking a black man in his 20s, slim, who was wearing a black puffa jacket and grey stonewash-coloured jeans.

A police spokesman said: “An 18-year-old woman had arranged to meet the second victim, a 17-year-old male, to buy a mobile phone.

“During the exchange, they were approached by an unknown male on a bicycle said to have been carrying a machete.

“He demanded the mobile phone and money from the woman, and kicked and swung the weapon at the 17-year-old male. He was not seriously injured. The suspect made off. Our enquiries continue.”