Police have issued a CCTV appeal after a man was spotted “touching himself inappropriately” on a Northern line Tube train.

The incident happened about 8pm on April 17 onboard a southbound train on the Charing Cross branch between Embankment and Kennington.

A man got on the last carriage of the train at Embankment and was seen by other passengers nearby putting his hand down his trousers and touching himself.

The behaviour continued for several minutes until the man got off the train at Waterloo and boarded a Morden-bound train.

Detective Constable Allan McTaggart, of British Transport Police’s sexual offences unit, said: “Who is the man in the suit? We want to speak to him as we believe he may have important information about what happened.

“If you know who he is, or witnessed the incident and have not yet come forward, please get in touch with BTP as soon as possible.”

Anyone with information should call police on 0800 40 50 40, or text 61016, quoting reference T/B5 of 15/05/2015. Information can also be passed anonymously to Crimestoppers on 0800 555 111.

A man was subsequently arrested and appeared on trial at Blackfriars Court but was found not guilty of the charge of outraging public decency.