The monarch was handed the sword by Edward Bolitho, the Lord-Lieutenant of Cornwall, to cut a large cake in celebration of the Big Lunch initiative at the Eden Project.
Although she was told by an aide that a conventional knife was available for use, the Queen replied: “I know there is, this is more unusual”.
Camilla assisted the in cutting through the final part of the cake.
Patrick Stewart, executive director of the Eden Project, an educational charity and eco-destination in Cornwall, said of the royals’ visit: “It is like comets — they don’t come around very often”.
“The important thing for me was there was every reason not to do it.
“The fact that they judged that with the eyes of the G7 that there was an opportunity — with the risk of missing trains and everything else — to be able to listen to some of the heartfelt stories of people here.
“It was absolutely priceless.”
The Big Lunch is an annual gathering of neighbours and communities at the Eden Project, where people are encouraged to get to know one another, while sharing food and building friendships. It was launched in 2009 with The Duchess of Cornwall is a patron of the event.
During the coronavirus pandemic, the Big Lunch has been virtual, but next year it is set to be an official part of the Queen’s Platinum Jubilee celebration in May.
The 20 guests this year were local volunteers who had been nominated for their services; among them were care workers who were on the frontlines of the Covid-19 pandemic. The Queen thanked them for the support that they had given to those in need in their communities during the pandemic.
The Queen also hosted an open-air reception at the Eden Project, where she was joined by G7 world leaders and the Prince of Wales, the Duchess of Cornwall and the Duke and Duchess of Cambridge.
German Chancellor Angela Merkel, US president Joe Biden, and Canadian prime minster Justin Trudeau were all photographed speaking with the royals, and a socially distant picture was taken to commemorate the gathering.
Again, the Queen brought about laughter when she asked the world leaders: “Are you supposed to be looking as if you’re enjoying yourself?”
To which Boris Johnson replied: “We have been enjoying ourselves — in spite of appearances.”