For "preliminary investigations"
Britain's Queen Elizabeth spent Wednesday night in hospital, for what Buckingham Palace has called "preliminary investigations".
The British monarch had cancelled a visit to Northern Ireland after being told to rest by doctors.
At the time Buckingham Palace said she "reluctantly" accepted guidance "to rest for the next few days".
A spokesperson insisted the 95 year-old was "in good spirits and is disappointed" that she will no longer be able to visit.
The British royal had been due to carry out a number of engagements on Wednesday, as well as attending the event in Armagh on Thursday which marked the centenary of partition.
The statement from the Royal family concluded with Queen Elizabeth extending her warm wishes to the people of Northern Ireland, adding she looks forward to visiting soon.
It is the first time she has been admitted to hospital since 2013.
Sky's Royal Correspondent Rhiannon Mills says it's not surprising, giving her busy work schedule:
Britain's longest reigning monarch has since returned to Windsor Castle.
She will continue to rest & carry out "light" duties.
Victoria Murphy, a royal commentator, says Queen Elizabeth II will have wanted to get back to normal as soon as possible:
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