THE Queen is said to be in good spirits as she recovers in hospital after she was admitted with a stomach bug.

She was received by King Edward VII's Hospital in London yesterday as a precaution after being struck down with the symptoms of gastroenteritis last week.

Officials at Buckingham palace said that the 86-year-old was not bed-ridden, but was "up and about" and receiving treatment.

It is the first time the Queen has had to stay in hospital overnight since she had a routine knee operation 10 years ago.

She became ill with the bug on Friday and was forced to pull out of engagements for the coming week.

After cancelling a visit to Wales on Saturday she chose to rest at Windsor, but was admitted to hospital last night as a "precaution".

The Queen was well enough earlier in the day to meet an employee privately to award her a medal for long service.

Her spokesman said she is likely to stay at the hospital for two days, and the interruption to her schedule meant that she had been forced to cancel a visit to HMS Lancaster in London today.

Other engagements have had to be postponed or reorganised. A reception for MPs and MEPs at Buckingham Palace will now be hosted by another member of the royal family, while a two-day tour to Rome with the Duke of Edinburgh, due to begin on Thursday, has also been called off to allow the Queen to rest.

Gastroenteritis causes inflammation of the stomach-lining and intestines, and symptoms can include vomiting, fever and stomach ache.

The Queen's treatment, which has not been disclosed, could include rehydration and tests to establish if the illness has been caused by an infection or if there is an underlying problem.

A palace spokesman said: "The Queen is being assessed at the King Edward VII's Hospital, London, after experiencing symptoms of gastroenteritis.

"As a precaution, all official engagements for this week will regrettably be either postponed or cancelled."

The spokesman 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."

It is believed the Queen will not be taking visitors, so as to cause minimal fuss. Downing Street said Prime Minister David Cameron had passed on his best wishes to the Queen.

A group of police officers stood guard at the entrance to the hospital, while a pack of television crews, photographers and reporters waited outside.

The Queen has undertaken a number of engagements during the past week. On Tuesday she met the Archbishop of Canterbury at Buckingham Palace, and on Thursday she presented a host of Olympic stars with honours during an investiture ceremony.