Witnesses are still being sought to an attack which left a woman in hospital with facial injuries.
Police were called out to the playing fields off Braywick Road on Thursday after the victim was approached by a man and assaulted at about 10am.
An unknown chemical was used during the attack, which is being treated as an isolated incident. The victim is still in hospital.
The offender is believed to have been wearing jeans and a black top.
Call police on 101 or Crimestoppers anonymously on 0800 555111.
Top Ten Articles
An extra £20,000 looks set to be allocated by the Royal Borough to fund a legal fight if Heathrow Airport is given permission to expand.