British Transport Police (BTP) is appealing for information after verbally abusing and pushing a rail worker.
The incident happened at around 7.50am on Thursday July 18 at Cardiff Queen Street train station.
Officers have released CCTV images of a person they would like to speak to.
He is described as white, of stocky build with dark cropped hair, and was wearing a purple T-shirt and grey three-quarter length jogging bottoms.
Investigating officer PC Dave Miles said: “A dispute between a passenger and a member of staff near the ticket barriers at Cardiff Queen Street rail station developed into an altercation, during which the victim was verbally abused and threatened.
“The man left the station immediately after but soon returned and subjected the victim to further verbal abuse before pushing him away.
“Although uninjured, the member of staff was understandably upset by the behaviour of the man, which was entirely unacceptable. Staff have the right to go about their work without suffering abusive and threatening behaviour.
“We’ve made a number of enquiries to try to identify this man, but to no avail.
“Therefore, I would ask anyone who recognises him to come forward, as we believe he may have information which could prove vital to the investigation.
“Aggression or violence towards rail staff will not be tolerated by BTP and the rail industry, and we will do everything we can to bring offenders to justice. I would like to appeal to anyone who may have witnessed the incident or who may recognise the man pictured to contact police.”
Anyone with information should contact British Transport Police on 0800 40 50 40 quoting background reference B13/WCA of 29/08/2013. Information can also be passed to the independent charity Crimestoppers on 0800 555 111.