The Duke of Edinburgh was last night under surveillance in the world-famous Papworth Hospital after emergency surgery for a blocked coronary artery. After ‘precautionary’ tests, Philip underwent what was described as a ‘minimally invasive procedure’ known as coronary stenting.

Dr Simon Davies, a cardiologist at the Royal Brompton Hospital in London, said: ‘It meant that the pain was from the heart. It means that one or more of the coronary arteries was badly narrowed or perhaps blocked. Buckingham Palace said in a statement last night: ‘His Royal Highness the Duke of Edinburgh was taken to Papworth Cardiothoracic Centre this evening from Sandringham House for precautionary tests after experiencing chest pain.

‘Following tests at Papworth the Duke of Edinburgh was found to have a blocked coronary artery which had caused his chest pains. This was treated successfully by the minimally invasive procedure of coronary stenting. Prince Philip will remain in hospital for observation for a short period.

Every senior member of the Royal Family was at the estate yesterday, including Prince Charles, the Duke and Duchess of Cambridge, Prince Harry, the Duke of York, Princess Anne and the Earl and Countess of Wessex. On Christmas morning the family go to church. In recent years Philip has continued to make the mile-long walk from the house, unlike the Queen, who is chauffeur-driven.

And Philip always organises the Boxing Day shoot at Sandringham. Mr Arbiter, who is Sky's royal commentator, told the broadcaster: 'He has had these chest pains before and I don't think it's anything untoward, but given his age they are being safe rather than sorry. 'I am sure we are going to see him on Christmas Day and he can look forward to accompanying the Queen in the new year.' Margaret Holder, a royal commentator, told the BBC: 'It's obviously very worrying for the Queen and the rest of the Royal Family who are gathering at Sandringham for Christmas.

By John Stevens
Stents are small metal tubes that are put into the arteries to help blood flow.

They are used to treat the type of coronary artery blockage that the Duke of Edinburgh suffered.

Every year, around 85,000  Britons are fitted with the  devices, which look like small pieces of scaffolding.

They are inserted into the artery during keyhole surgery and then expanded to widen the artery.

During the procedure a hollow tube containing the stent along with a small inflatable balloon is passed into an artery through the groin or arm.

The operator then uses X-ray screening to direct it into a coronary artery until it reaches the narrow or blocked section. The balloon is then gently inflated expanding the stent so it holds the narrowed blood vessel open.

When it is fully expanded the balloon is let down and removed, leaving the stent in place.

Most people can go home the same day or next day, but if it has been an emergency procedure, stays in hospital are usually longer. Sometimes there is a small amount of bleeding after the procedure.

In the majority of cases, people find that they feel back to normal after just a few days, but if the stent has been put in after a heart attack the recovery takes longer.However, in some cases the rigid metal can cause the walls of the artery to become inflamed or damaged, and scar.

In recent years, drug-eluting stents have been developed. These are coated with a tiny amount of a drug which is delivered to the area around the stent to prevent the scarring process and thus stop the artery from narrowing.

A new type of stent, called bioresorbable vascular scaffold, is currently being developed that is made of corn starch rather than metal. It gradually disappears over two to three years, so once the artery has been able to return to normal, the stent is metabolised by the body.

Stents cost up to £900 each, depending on the type used.