Searches for a woman who police believe may have been murdered are being carried out in Windsor Great Park.
Joanna Brown, 46, who runs a bed and breakfast from a mansion in Ascot, was reported missing on Monday morning.
Her husband Robert Brown has been arrested by officers on suspicion of her murder.
An earlier search of the mock-Tudor guest house, which borders Windsor Great Park, led police to believe the mother-of-two may have come to harm.
The park, owned by the Crown Estate, covers 5,000 acres (20 sq km) and is home to The Queen's Berkshire residence of Windsor Castle. Most areas are open to the public.
Police said they had received new information on Thursday afternoon that had led them to the park, but released no further details.
On Wednesday, officers were given an extension to question Mr Brown until Friday morning.
'Loved and admired'
Mrs Brown's family has appealed for information, saying she is a "very special person, loved and admired by everyone who knows her, a wonderful and caring mother to her two children".
In a statement they added: "This is a very difficult time for our family.
"We ask that anyone with any information about the whereabouts of Joanna contact the police."
A family member raised the alarm on Monday after failing to contact Mrs Brown.
Officers later received more information and her husband was arrested at his home in Winkfield.
Det Ch Insp Steve Tolmie, leading the investigation, said searches of Mrs Brown's home, described on its website as "a beautiful English country home", were continuing.
A search of a large pond in the grounds has already been carried out.