Queen Elizabeth II spent Wednesday night in hospital for “preliminary investigations”, Buckingham Palace said on Thursday night.
The 95-year-old Queen returned to Windsor Castle on Thursday afternoon, and remains in “good spirits”, the palace added.
“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,” said a Buckingham Palace spokesman quoted by PA Media.
The monarch had been ordered to rest by doctors and advised to miss a trip to Northern Ireland earlier this week.
It is understood the trip to hospital on Wednesday afternoon was expected to be for a short stay for some preliminary investigations, so it was not announced by the Palace at the time, as well as in order to protect the Queen’s medical privacy.
The overnight stay was said to be for practical reasons, according to PA Media.