On Friday 22 April two men were speaking to the victims, a man and a woman, on a platform at Lincoln station before boarding the 9.30pm service to Harborough.
Once on the train, they sat together and an altercation broke out. One of the men punched the other man on his neck, and when the two victims got up to leave the other man sexually assaulted the woman.
If you recognise them, or have any information, please contact BTP by texting 61016 or calling 0800 40 50 40 quoting reference 302 of 23/04/22.
Alternatively, you can call Crimestoppers anonymously on 0800 555 111.
