Two teenagers approached a boy on a train on October the 9th and demanded he hand over his phone, inferring they had a knife.
The two boys made the teenager get off the train at Clapham Junction where they made him sign out of his iCloud account.
They then stole his phone.
Detectives would like to speak to those involved as they believe they may have information which could help with their investigation.
Anyone who recognises them is asked to contact British Transport Police by texting 61016 or by calling 0800 40 50 40, quoting reference 714 of 9 October.
You can also contact Crimestoppers anonymously on 0800 555 111.
