Two students were robbed from behind by a knife-wielding man riding a bike along the Grand Union Canal pathway.
Police have released an e-fit image of a man they want to speak to in connection with the robbery.
Two 18-year-old men were targeted in Spikes Bridge Park, Southall, on Tuesday June 16, just after 5.30pm.
Police have only this week released the e-fit and the appeal.
The suspect is said to have threatened the pair with a knife before taking their wallets and phones. He then rode off along the pathway in a northerly direction around the bend where the men lost sight of him.
He has been described as a white man, 30 to 35-years-old, 6ft tall, with short light brown hair and stubble.
No arrests have been made and enquiries continue.
Anyone with any information is asked to call Ealing CID on 101 or anonymously through Crimestoppers on 0800 555 111.
