British Transport Police (BTP) would like to speak to this man in connection with an assault and theft which happened at Cardiff Queen Street train station.
Two students were attacked after one had their iPhone stolen on Friday November 2.
Officers have released CCTV images of a man they believe may have key information which could assist their investigation.
Investigating officer PC Carl Needs said: “At around 1.15pm, two Chinese students were on the platform waiting for a train. One of them was using his iPhone when a man approached them and snatched the phone before running down the stairwell.
“They chased after the man and caught up with him in the subway, where he assaulted both students before making off via the front of the station.”
Having viewed CCTV footage, officers have identified a man they would like to speak to in connection with the incident.
He is described as white, in his early 20s, of slim build, clean shaven with short brown hair. He was wearing dark trousers, white trainers and a Fila hooded top.
“We’ve made local enquiries in an attempt to obtain a name for this man but have had no success so far,” said PC Needs.
“We believe he got off a Bargoed train at Queen Street station. I am hopeful that someone will recognise this individual, who we are extremely keen to speak to as we believe he may have key information that could assist us with this investigation.
“Also, if you’ve you been offered a 32GB black Apple iPhone 4S for sale recently, we would like to hear from you.”
If you recognise the man in the images, or have any information that could assist police with their enquiries, contact British Transport Police on 0800 40 50 40 quoting background log B3/WCA of 23/11/2012. Alternatively, call Crimestoppers anonymously on 0800 555 111.