Britain's Queen Elizabeth II spent Wednesday night in hospital for "preliminary investigations" after cancelling her visit to Northern Ireland, Buckingham Palace has confirmed in London.
The 95-year-old monarch had cancelled the trip planned for Wednesday and Thursday to rest for a few days at Windsor Castle.
The monarch returned to Windsor Castle at lunchtime on Thursday.
The Queen was seen by specialists at the private King Edward VII's Hospital in central London, PA Media reported late Thursday.
A Buckingham Palace spokesman said: "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."
"It is understood the trip to hospital on Wednesday afternoon was expected to be for a short stay for some preliminary investigations, so 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
A busy programme
The Queen has had a busy programme and hosted a global investment summit at Windsor Castle on Tuesday evening, where she was said to have looked cheerful as she carried out her royal duties.
The Queen, who is just five years away from her 100th birthday, is due to celebrate her Platinum Jubilee – 70 years on the throne – next year.
The monarch's husband of 73 years, the Duke of Edinburgh, died in April at the age of 99.
Last week, she used a walking stick at a major public event when she attended a service marking the centenary of the Royal British Legion, PA reported.
The monarch's admittance to hospital is understood not to have been related to the coronavirus.
