Britain's 95-year-old Queen Elizabeth spent a night in hospital for what Buckingham Palace termed 'preliminary investigations' but returned to Windsor Castle on Thursday and was in good spirits.
The monarch cancelled an official trip to Northern Ireland on Wednesday with the palace saying she had been told to rest by her medical staff, and that it was not related to COVID-19.
"Following medical advice to rest for a few days, the queen attended hospital on Wednesday afternoon for some preliminary investigations, returning to Windsor Castle at lunchtime today, and remains in good spirits," the palace said in a statement.
A royal source said the queen had stayed in hospital for practical reasons and that her medical team had taken a cautious approach.
She had returned to her desk for work on Thursday afternoon and was undertaking some light duties, the source said.
Elizabeth spent Tuesday night hosting a drinks reception at Windsor Castle for billionaire business leaders such as Bill Gates after Prime Minister Boris Johnson convened a green investment conference ahead of the COP26 climate summit.
The queen, the world's oldest and longest-reigning monarch, had appeared in good health then, smiling happily as she met the guests.