Overview
- Police say a group threatened an elderly man on a Metropolitan Line train just before 11pm on 29 December as it approached Northwick Park.
- Another passenger who intervened was slashed in the face with a knife, leaving a cut above his eyebrow.
- The group stole the victim's bag and fled from Northwick Park Underground station in North London.
- Investigators have released images of five men they want to identify and have urged the public to help the inquiry.
- Information can be sent to BTP by texting 61016 or calling 0800 40 50 40, quoting 607 of 29 December, with anonymous tips accepted by Crimestoppers on 0800 555 111.