LONDON (AP) — Buckingham Palace says Queen Elizabeth II spent a night in a hospital after being advised by her doctor to rest.

The palace says the 95-year-old British monarch went to the hospital for “preliminary investigations.”

It said she returned to her Windsor Castle home at lunchtime on Thursday, “and remains in good spirits.”

On Wednesday, the queen canceled a scheduled trip to Northern Ireland.

The palace said she had “reluctantly” accepted medical advice to rest for a few days. It did not elaborate.

Britain’s longest-lived and longest-reigning monarch, Elizabeth is due to celebrate 70 years on the throne next year.