A passenger was knocked unconscious during an unprovoked attack on a train.

The victim, a 44-year-old man from Witham, was travelling on a service from London to Southend Victoria on November 15.

Police are appealing for help tracing three men they suspect carried out the attack.

The trio boarded the train at Stratford station and stood in a walkway near where the victim was sitting.

Sergeant Emma Weir said: “As the train pulled out of the station the three became abusive towards the victim – calling him names and swearing at him repeatedly.

“When he asked them to leave him alone one of the group became violent and punched the victim once with an uppercut.

“We believe this happened as the train passed through Romford station and the ferocity of the assault left the victim unconscious.”

The assault is believed to have taken place at about 6.15pm.

Ms Weir said: “The victim regained consciousness shortly before the train arrived at Rayleigh rail station, whilst the suspects seemed to have left the train – possibly at Shenfield, Billericay or Wickford.

“This was an unprovoked assault on a man who was minding his own business and was simply trying to get home.

“I am determined to trace those responsible and am calling on the public to come forward with any information.”

The suspects were all white and aged in their late 20s.

The first suspect was about 5ft 10in, stocky, with short blonde hair, unshaven and wearing blue jeans, a dark blue hooded top and white trainers.

A second man was about 5ft 9in, thinner than the first suspect, with brown hair and wearing blue jeans, a black Superdry hooded top and a black baseball cap with an NY logo.

The third man was also wearing jeans and trainers - the victim believes he was also wearing a Superdry hooded top and a red baseball cap.

Anyone who recognises the descriptions of the suspects or has any information about the incident should call British Transport Police on 0800 40 50 40 or Crimestoppers anonymously on 0800 555 111.