The Queen is in "good spirits" and "good health" besides the symptoms of gastroenteritis, her spokesman has said. He added:
This is a precautionary measure. She was not taken into hospital immediately after feeling the symptoms. This is simply to enable doctors to better assess her.
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Last minute preparations are going on at the Church of St Mary Magdalene where Princess Charlotte will be christened.
Princess Charlotte is being christened on Sunday at Sandringham in Norfolk in only her second public appearance since she was born.
Thunderstorms clear the North, leaving a dry and warm day with sunny spells.