British Transport Police officers have released a CCTV image of a man they want to trace after a 66-year-old woman was sexually assaulted at Waterloo Underground Station.
Detective Constable Suleman Yazdani said: "Around 6.40pm on Wednesday 3 December, the victim exited the ticket barriers and was making her way to the mainline station.
"She noticed a man walking towards her from the other direction, and stepped towards the wall to avoid him.
"The man deliberately walked into the woman, sexually assaulting her before barging her out of the way and making his way to the barriers."
The woman considered following him, but decided against it, and reported the incident to station staff instead.
DC Yazdani said: "I am pleased the woman came forward. I would encourage anyone who believes they have been the victim of unwanted sexual behaviour on the tube or railway to do the same.
"I believe the man in the image we have issued today can help us with our investigation into the assault. Who is he?"
Anyone with information is asked to contact British Transport Police on 0800 40 50 40, or text 61016, quoting reference TSUB/B10 of 05/01/2015. Information can also be passed anonymously to the independent charity Crimestoppers on 0800 555 111.