A man has been arrested and bailed after a sexual assault on a train in the Cynon Valley.
The man, who was in a group, first made lewd comments towards the male victim as they walked past - before sexually assaulting him.
British Transport Police said the man then "made light" of the situation before he was arrested in Abercynon.
Officers are now appealing for witnesses. It happened at around 12.50pm on Saturday 1 July.
The train from Aberdare was travelling to Cardiff Central and the sexual assault took place between Penrhiwceiber and Abercynon stations.
British Transport Police officers boarded the train in Abercynon and arrested a 40-year-old man in connection to the assault. He is currently on bail as officers continue their investigation.
Police want to hear from anyone who was witness to the assault or has any information that would assist their enquiries.
Anyone with information is asked to contact BTP by texting 61016, or by calling 0800 40 50 40 quoting reference number 2300075449. Alternatively, call Crimestoppers anonymously on 0800 555 111.