Detectives want to speak to this man in connection with a sex assault on a train between East Croydon and Brighton.
British Transport Police are appealing for information about the incident, which happened at about 8.55pm on Wednesday, March 7.
The 27-year-old victim, from Brighton, boarded the train at East Croydon and felt a man, who was sat opposite, touch her indecently.
After immediately leaving her seat, the victim noticed the man had his camera phone out and was either photographing or videoing her as she walked away.
The man then left the train when it arrived at Three Bridges.
Investigating officer, Detective Constable Vanessa Cottington, said: "The man's actions were completely unacceptable and understandably the incident left the victim upset and distressed.
"We have followed a number of avenues of enquiry for this incident, including circulating the man's image on police intelligence systems, but to no avail so far."
Anyone with information should contact BTP on 0800 40 50 40 quoting reference B8/LSA of 25/04/12. Alternatively contact Crimestoppers anonymously on 0800 555 111.