A nurse was sexually assaulted as she used a hospital toilet while on duty, police have revealed.
The woman was attacked at the Princess Royal University Hospital, near Orpington, in south-east London.
A Scotland Yard spokesman said: "We are investigating a sexual assault on a woman in a toilet at a hospital that occurred at around 1830 on Saturday."
Detectives from Bromley CID said they are looking for a white man with a London accent.
Additional security has been put in place within the hospital while the incident is being investigated, Bromley Hospitals NHS Trust confirmed.
"We continue to work with our partner organisations to ensure the protection of staff," said a trust spokeswoman.
The Royal College of Nursing (RCN) said such an attack is "extremely disturbing".
"The RCN is appalled to hear about this attack on a member of staff," said Bernell Bussue, RCN London regional director.
"Such a serious incident warrants full and swift action against the perpetrator."
He said the RCN has expressed growing concern about "the increasing incidence of violence towards healthcare staff".
A quarter of all prosecutions involving violence against NHS staff were in London, according to figures released by the NHS in November.
The statistics found that 219 people were prosecuted for attacking hospital staff in the city in 2004.