The Duke of Edinburgh is spending a few days in hospital as a precaution after feeling unwell, Buckingham Palace has said.

Philip, aged 99, who received a Covid-19 jab in January, was admitted to the private King Edward VII’s Hospital in London on Tuesday evening, on the advice of his doctor, for “observation and rest”.

There will be concern for the duke because of his age – the Queen’s consort turns 100 on June 10 – but it is understood he walked into hospital unaided and is said to be in “good spirits”.

The duke’s illness is not Covid-related and it is understood he had been feeling unwell for a short period before the doctor was called, and he was not an emergency admission but travelled to hospital by car.

The Queen has remained at Windsor Castle working as normal and earlier spoke by telephone with the First Sea Lord, Admiral Tony Radakin, about the work of the Royal Navy at home and overseas.

A spokesman for Prime Minister Boris Johnson said: “The PM sends his best wishes to the Duke of Edinburgh as he undergoes a few days of rest in hospital.”

Philip has been spending the latest lockdown with the Queen at Windsor Castle after they decided to have a quiet Christmas and remain at their Berkshire residence rather than have a family gathering at Sandringham.

Buckingham Palace said in a statement: “His Royal Highness the Duke of Edinburgh was admitted to King Edward VII’s Hospital in London on Tuesday evening.

“The duke’s admission is a precautionary measure, on the advice of His Royal Highness’s doctor, after feeling unwell.

“The duke is expected to remain in hospital for a few days of observation and rest.”

It is understood the decision to admit Philip was taken with an “abundance” of precaution.

The morning after he was admitted, the Prince of Wales and Duchess of Cornwall – who have received their Covid jabs – visited the Queen Elizabeth Hospital in Birmingham and chatted to patients who have also received their vaccinations.

Charles and Camilla were aware of Philip’s hospital admission before their trip, and the duchess told vaccination trial staff “I leapt for joy. I didn’t feel anything” after having her jab.

Philip last had a spell in hospital when he spent four nights at the King Edward VII’s in December 2019, where he was treated for a “pre-existing condition” and discharged on Christmas Eve.