LONDON: Questions mounted on Friday about the health of 95-year-old Queen Elizabeth II after she had tests and spent a night in hospital, despite royal officials saying she was resting at home.

Buckingham Palace said on Wednesday morning that she pulled out of a planned engagement in Northern Ireland and had been advised to rest on medical advice.

But royal officials conceded late on Thursday that she had in fact had “some preliminary investigations” in hospital on Wednesday, and stayed overnight, after The Sun newspaper broke the news.

She returned from King Edward VII’s Hospital in central London to her Windsor Castle home west of the capital and was said to be “in good spirits”.

Prime Minister Boris Johnson sent his best wishes, his spokesman said, while members of the public near her Buckingham Palace home in central London said they were unperturbed.

Kirsty Duffield, an operations manager, told AFP health checks were “quite normal” at the Queen’s age and it was “really positive” that she was released so quickly.

Housewife Katie Lavin pointed out the monarch was still riding horses and appeared strong and independent, even though it was clear she was “getting a little bit fragile”.

Visiting US theatre director Charles Fee said she would be described as “a tough broad” across the Atlantic.

Britain’s Press Association news agency said the hospital visit and stay was not initially disclosed because it was expected to be short, and to protect her privacy.

She stayed overnight for “practical reasons”, said to be because it was too late to make the 26-mile (42-kilometre) trip back to Windsor.

The Queen has previously been treated at the exclusive private clinic, which is known for treating the royal family, including in 2013 for gastroenteritis, when she also stayed for one night.

The development follows several busy weeks during which the monarch undertook more than a dozen public engagements, including hosting a reception on Tuesday for global business leaders at Windsor Castle.