A group of people threatened an elderly man on a Metropolitan line train to Northwick Park soon before 11pm on December 29.
Another passenger intervened and was attacked by the group, being slashed with a knife above his eyebrow.
The group then fled Northwick Park Underground station having stolen the man’s bag.
Detectives are appealing for anyone who recognises the men pictured, or who may have witnessed the incident, to make contact.
Anyone with information can contact BTP by texting 61016 or by calling 0800 40 50 40, quoting reference 607 of 29 December.
You can also contact Crimestoppers anonymously on 0800 555 111.
