A man was sexually assaulted on a London Underground service after checking if he was on the right train.
Police said a passenger got on a northbound Northern Line Tube at Kennington at the same stop as another man.
The passenger asked if he was on the correct train at which point he was sexually assaulted. He then moved to another carriage.
Officers have released an image of a man they want to find.
Britis Transport Police said: "Officers believe the man in the image may have information which could help their investigation.
"If you recognise him, or have any information, please contact BTP by texting 61016 or calling 0800 40 50 40 quoting reference 2300092243.
"Information can also be given anonymously to Crimestoppers on 0800 555 111."
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