On Saturday, July 16, around 6pm, two men approached a 17-year-old girl on the service and began making inappropriate sexual comments to her.
One of the men then inappropriately touched the victim before inviting her to a hotel with him. A number of passengers witnessed the incident and stepped in to help.
Both men were discharged from the service at Scunthorpe railway station.
Officers are eager to speak with anyone on the train who witnessed the incident because they may have information that is critical to the investigation.
Witnesses or anyone with information should contact BTP by texting 61016 or calling 0800 40 50 40 and referencing reference 722 of July 16.
You can also call Crimestoppers at 0800 555 111.
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