A pensioner and a 25-year-old woman were among those targeted in a series of terrifying attacks on south London trains and stations throughout April.
British Transport Police believe three terrifying incidents that took place last month are connected and have now released a CCTV image, pictured, of a man they want to identify.
The first robbery took place on a train from London Bridge station at around 7.10pm on Tuesday, April 9, when a 52-year-old man was approached by another, unknown man, who asked for the time.
The attacker then indicated he was carrying a knife and demanded his phone. The victim handed it over before attempting to get it back but the assailant repeatedly hit him in the head and ran off the train.
The next day (Wednesday, April 10) at around 3.10pm, a 72-year-old man was on a static train on Platform 11 at London Bridge station.
A man approached him and snatched his phone before threatening to stab him when he tried to grab it back. The assailant then ran down the carriages and off the train.
On Thursday, April 11, at around 3.10pm, a 25-year-old woman was on a train from Honor Oak Park to Clapham Junction. A man walking along the carriages approached her and asked for the time before demanding her phone, earpods and case, threatening to stab her if she did not comply. She handed over her belongings over and the man left the train at Crystal Palace.
Officers say the man in the CCTV image he could have information that will help the ongoing investigation, and have urged him or anyone who can identify him, to get in touch.
Anyone who recognises the man is asked to contact BTP by texting 61016, or by calling 0800 40 50 40 quoting reference 504 of 11 April.
Information can also be given anonymously to Crimestoppers on 0800 555 111.