British Transport Police officers are searching for a man who they believe could have vital information about the theft of a laptop.
The incident occurred at around 10.45am on Monday, January 5 on board a train from London Euston that passed through Preston.
Investigating officer Glyn Thomas said:“The victim boarded the 9.30am Euston to Glasgow Central service and sat in coach F.
“He placed a black bag containing a laptop and personal items on the seat next to him, by the aisle.
“Another man, who also boarded at Euston, took a seat at the end of the carriage, facing the victim.
He continued: “When the victim fell asleep, the man walked down the aisle and picked up the bag.
“He then walked further down the carriage and took a seat.
“Both men left the train at Preston station at around 12:10 pm.”
Officers believe the man in the image could have information vital to their enquiries and urge him or anyone who recognises him, to come forward.
Anyone with information should contact British Transport Police on 0800 40 50 40 or text 61016 quoting background reference PSUB/B6 of 13/01/2015.
Information can also be passed to the independent charity Crimestoppers anonymously by contacting them on 0800 555 111.