The latest attack was on Wednesday night, when a 23-year-old woman was dragged to the ground and sexually assaulted while walking from the nurses' hostel to the social club.
Hospital managers have sent letters to staff on the Broadmoor estate, warning them it is not safe for women and children to go out alone at night.
Alan Franey, Broadmoor general manager, said that he was very worried by the man's attacks but thought it "improbable'' that he was a former patient. "The latest attack was very serious and we're pulling out all the stops to protect staff and ensure thisman is caught," he added.
The attacker is thought to lurk in the forest adjoining Broadmoor, picking on women as they leave the hospital.
In Wednesday's incident, a woman who works in the staff kitchens was pounced on by a man who leapt out of the dark.
A colleague said: "Had she not managed to get away, we are certain she would have been raped."
Another attack involved a girl aged 15 and her 13-year-old brother, who escaped after being were chased by a man.
A Thames Valley Police spokesman said: "It is too early to say whether the attacker is a former patient or someone who has some other connection with Broadmoor."Reuse content