Police have launched an investigation after a man exposed himself on board a train service between London Victoria and Haywards Heath.

A woman was on board a train from London Victoria station heading towards Brighton at 8.25am on August 20, and police said she began to feel uncomfortable when two men began staring at her after sitting in her vicinity.

Prior to the train arriving at Haywards Heath station, it is alleged one of the men stood up and exposed himself through the seats and touched himself inappropriately while looking towards the victim.

Police said the second man had moved to observe the incident before both men got off at Haywards Heath.

British Transport Police have released a CCTV image of a man they believe to have vital information which could assist in the investigation, and would like to speak with anyone who may have been on the journey that day and witness what happened.

Anyone with information should contact the British Transport Police on 0800 40 50 40, or text 61016 and cite the reference 292 of 20/08.