Five people have been arrested after a brawl on a train last night which left one man unconscious.

A 23-year-old man was attacked after going to the assistance of a conductor being harassed on the Thameslink service just before 9pm.

A gang of youths set on him and kicked him unconscious. He also suffered facial injuries.

The train was stopped at Hassocks station and the youths ran off.

Police, including the force helicopter, searched the area and five youths were later arrested in and around Hassocks station.

Sergeant Gary Ansell of British Transport Police in Brighton said: "The incident happened on the Thameslink train heading towards London.

"There was a disturbance en route where a conductor on the train was having problems with a group of youths.

"A member of the public and his friend went to intervene on the side of the conductor and were assaulted.

"The main victim, a 23-year-old man from London, was kicked unconscious and received facial injuries.

"He was taken to the Princess Royal Hospital and kept in overnight. His facial injuries were found to be a badly cut lip and he was expected to be released today."

Sgt Ansell said a gang of youths ran off at the station and Sussex Police began a search for them.

The other passengers on the train waited at Hassocks Station and boarded other services which were held up behind the Thameslink train.

Five youths have been detained overnight at Crawley police station and were due to be questioned about the incident today.