Have you seen this man? (Credit: Metropolitan Police)
The incident happened at around 7.30pm on Sunday, 20 February 2020.
A girl in her mid-teens and a man boarded a number 99 bus at Woolwich DLR station and went to the upper deck.
They did not know each other and as the bus travelled towards Bexleyheath the man engaged the girl in conversation.
He then allegedly carried out a sexual assault by inappropriately touching the girl.
After the assault, the man got off the bus at Plumstead Manor Way.
Detectives have described him as aged 18-25, 5ft 10in and of Asian appearance.
Any witnesses or anyone with information is asked to call police on 101 quoting CAD 1837/22FEB.
To give information anonymously contact Crimestoppers on 0800 555 111 or online at crimestoppers-uk.org.
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Tags: Sexual Assault, Metropolitan Police, Woolwich