THE Queen spent Wednesday night in hospital for “preliminary investigations”, Buckingham Palace has said.

The 95-year-old monarch, who was ordered to rest by doctors and advised to miss a trip to Northern Ireland, returned to Windsor Castle at lunchtime yesterday and remains in “good spirits”.

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.”

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The head of state’s trip to central London’s private King Edward VII’s Hospital, which began on Wednesday afternoon, was kept a secret but the Palace issued a statement last night after The Sun newspaper broke the news.

It was the monarch’s first overnight hospital stay in eight years.

It is understood the Queen was due to attend for only a short stay while she was seen by specialists, so the development was not announced by the Palace at the time, and protecting the Queen’s medical privacy was also a consideration.

The overnight stay was said to be for “practical reasons”, a source said.

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The Queen’s team of royal physicians are understood to have been taking a “cautious approach”.

The Queen was said to be back at her desk yesterday afternoon, undertaking light duties.