A woman was sexually assaulted while on board a train between Leeds and Sheffield.
The assault happened between 4.35pm and about 4.50pm on Tuesday, March 26 on the train from Sheffield to Leeds Station.
A man boarded the train at Darton rail station - the stop before Wakefield Westgate - and sat next to the woman.
Wanted: 16 people police urgently want to speak to in Wakefield
He began trying to make conversation.
The man went on to touch the woman's knee, put his arm around her and squeeze her shoulder.
When she tried to leave, he pulled her back and attempted to kiss her.
The woman managed to get away from the man and walked down the carriage to sit with two other women.
One of the women took a photo of the suspect and police are keen to speak to this woman.
West Yorkshire schoolteacher admits to serious child porn offences and told to expect jail "for a very long time"
The man is described as dark-haired, olive-skinned and aged in his mid-30s.
He is described as slim, tall and wore a black and white chequered hat, a brown and beige scarf and brown clothing.
He spoke in broken English.
British Transport Police officers want to speak to anyone who witnessed the offence.
They particularly want to speak to the woman who took the photo of the suspect.