A passenger grabbed a ticket inspector by the throat on a train from Aberdeen to Dundee.

British Transport Police said the 35-year-old man was attacked by another man in his mid 50s for "no apparent reason" as the 10.27pm Aberdeen to Dundee train approached Portlethen station at about 10.40pm.

Officers have reviewed CCTV footage and discovered the man responsible, who got off the train at Laurencekirk at about 11pm, was dropped off at the same station at about 1.30pm that day by the driver of a silver estate car.

A spokesman for the BTP said: "Around 10.40pm, the 35-year-old male member of staff was grabbed around the throat by a man in his mid 50s for no apparent reason as the train approached Portlethen station.

"The suspect, who is described as being bald, heavy build and wearing a black jacket, black trousers, a blue shirt and a black scarf, got off at Laurencekirk just before 11pm."

Constable Nicky Ritchie is appealing for anyone who was on the train or at the station and has information which can help the enquiry to contact British Transport Police on 0800 405040 or by texting 61016.

Information can also be given anonymously to the independent charity Crimestoppers on 0800 555111.