Police are hunting for a man who grabbed a woman from behind, touched her and pulled at her clothes in Mitcham on Sunday morning.
The victim was followed from Colliers Wood tube station along Western Road before being sexually assaulted in Lowry Crescent at around 1.45am.
Police have said the 23-year-old bravely fought off her attacker and forced him to run away by shouting. They are now appealing for witnesses.
The suspect is described as a white man in his mid 20s. He was wearing jeans and a dark coloured shirt or t-shirt and is thought to have been 5ft 10ins.
Anyone with information should call Detective Constable Jakki Arden on 020 8649 3039 or Crime Stoppers on 0800 555 111
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