Officers have released new images in connection in connection with the offences
The two men boarded the service at Clapham Junction on 27 August at around 4.30pm.
At 4.41pm, the two men approached the victim sitting in another section of the train. One of the men threatened the victim with a hammer concealed in his sleeve and demanded the victim hands over his watch.
After taking the watch, the two men remained on the train and alighted when the train arrived at Isleworth station.
Officers believe the men in the CCTV images may have information which could help the investigation.
If you recognise them, or have any information, please contact BTP by texting 61016 or calling 0800 40 50 60 quoting reference 368 of 27/08/20.