Baroness Thatcher is in "good spirits" in hospital where she is being treated after breaking her arm in a fall, her son said.
Sir Mark Thatcher left Chelsea and Westminster Hospital, west London, after briefly visiting his mother.
Sir Mark said: "She had a very good night and was relaxed and slept well.
"She has had some painkillers but was in very good order and had a bit of mischief about her.
"She's in very good spirits."
Asked when his mother is likely to leave hospital, he said: "That is entirely a matter for the clinicians and we will have to wait and see."
The former Tory prime minister sustained the injury when she lost her footing at her London home.
Doctors decided to keep her in overnight as a precaution, having initially decided to discharge her earlier.
Lady Thatcher has suffered a number of health scares over recent years, including minor strokes.
