Prince William stepped in to represent the Queen at an investiture ceremony today after it was revealed that the monarch was suffering from some "mild discomfort" with her ankle.

Buckingham Palace insisted that the Queen was not unwell but had experienced a busy weekend of engagements including the Festival of Remembrance and the service of remembrance at the Cenotaph.

A spokesman said the 87-year-old would be fufilling a busy day of engagements tomorrow and is looking forward to her visit to Manchester on Thursday. It is understood that the Queen has not injured her ankle.

"The Queen is experiencing some mild discomfort with her ankle, following a busy weekend," a spokesman said.

William presided over the investiture, knighting Blackadder star Sir Tony Robinson and making former LIberal Democrat leader Sir Menzies Campbell a Companion of Honour.

The investiture ceremony was the second to be conducted by William, who carried out his first last month when he presented Wimbledon champion Andy Murray with an OBE.

Sir Tony, best known for his role as the downtrodden dogsbody Baldrick in the Blackadder series, revealed what William confided to him.

"He said that he was a big fan of Blackadder and was there going to be another series? I said we have always talked about it.

"I said to him 'Would you be prepared to be in it?'. He said 'Yes' like a shot," Sir Tony said.

Sir Tony, who was knighted for public and political service, also confessed that he experienced a "Baldrick" moment during the ceremony, forgetting to bow to William at the outset and then "going the wrong way" after he had been knighted.

Sir Menzies, who is to stand down as an MP at the next general election, was made a Companion of Honour, which is awarded for services of national importance.

He revealed that the front stud to his stiff collar for the ceremony had broken en route to Buckingham Palace. He said the Palace stepped in and produced a replacement - believed to belong to the Lord Chamberlain.

He said he and William chatted about St Andrews University, where he is chancellor. William is a graduate of St Andrews.

"He is very enthusiastic about supporting our 600th anniversary celebrations and I asked him about Prince George," Sir Menzies said.

"He said he was sleeping a bit more and that was helping everyone."