The Queen has joked with two of England’s rugby stars about the fitness levels of the UK’s players as she celebrated the achievements of the Commonwealth.

Brothers Billy and Mako Vunipola, who have Tongan heritage but were brought up in the UK, laughed when they said the Queen questioned the widely held view that today’s rugby sportsmen were tougher and fitter.

The monarch was hosting a Buckingham Palace reception for the Commonwealth diaspora in the UK and was joined at the event by the Prince of Wales and Duchess of Cornwall.

Prime Minister Theresa May and husband Philip made a surprise appearance as did Foreign Secretary Boris Johnson who earlier in the day had given a major speech on Brexit

Mako, who was part of the England team that beat Wales at the weekend in a Six Nations match, said: “She was saying that apparently rugby is getting a lot tougher now, everyone’s fitter but she can’t see it.

His brother quipped: “I think she was calling us fat – which is fair enough.”

The Queen greets Prime Minister Theresa May (Jonathan Brady/PA)The Queen greets Prime Minister Theresa May (Jonathan Brady/PA)

The event heralded the start of a series of major Commonwealth events this year culminating in a heads of government meeting for global leaders in London this April.

Billy, who has missed out on Six Nations rugby due to a broken forearm, said: “It’s a massive honour that we are here and a privilege, something we will probably brag to our mum about.”

The rugby-playing brothers towered over the Queen who spent almost two hours chatting to those invited to the palace reception.

Among the guests was celebrity chef Monica Galetti from New Zealand, Sheku Kanneh-Mason the 2016 BBC Young Musician of the Year, and Commonwealth Secretary-General Baroness Scotland.

The Queen speaks to Foreign Secretary Boris Johnson, left (Jonathan Brady/PA)The Queen speaks to Foreign Secretary Boris Johnson, left (Jonathan Brady/PA)

The heir to the throne’s appearance at the event came a day after the BBC claimed officials have been discussing who might succeed the Queen as head of the Commonwealth.

But the Commonwealth Secretariat has denied that a high level group of officials met in London to consider who might follow the monarch.

While many Commonwealth figures presume there will be no realistic alternative to Charles when he becomes king, there has in the past been talk of electing a ceremonial leader to improve the organisation’s democratic credentials.

The institution’s 53 member states represent 2.4 billion of the world’s population ranging from Canada and Australia to Jamaica, Malaysia and Tonga.

The Prince of Wales meets rugby players Mako and Billy Vunipola (Jonathan Brady/PA)The Prince of Wales meets rugby players Mako and Billy Vunipola (Jonathan Brady/PA)

During his tour of south-east Asia and India last autumn Charles spoke about the importance of the Commonwealth and the potential of the family of nations to make a difference to the major challenges facing the world.

The heir to the throne is likely to use the Commonwealth Heads of Government Meeting (CHOGM) in London in April as an opportunity to meet leaders and discuss common issues.

Just before the event began as guests were arriving, a man punched a police officer on duty outside the place gates and was arrested.

A Scotland Yard spokesman said: “The man assaulted an officer and a second officer sustained a minor injury detaining the man. Nobody required hospital treatment.”