Officers arrested the teenager, who matched the description of the suspect, in the park at 4pm on Friday 9 April. He was taken to a south London police station and bailed to return pending further enquiries on a date in late April.
It follows enquiries after reports that a male approached girls aged under 13 and exposed himself.
The first incident occurred on 31 December 2020 at around 5pm. A girl was approached by a male who first exposed himself and then attempted to sexually assault her. He ran off when the victim screamed.
The second incident happened on Tuesday, 2 March at approximately 4pm. A male exposed himself and performed a lewd act in front of two girls.
The third incident occurred on Sunday, 28 March at approximately 4pm. A male exposed himself to a girl.
Enquiries continue. If you have any information that could help the investigation please call police on 101 or tweet @MetCC providing the reference Op Primelea. Alternatively information can also be provided to Crimestoppers, anonymously, on 0800 555 111.