Dame Mary said she was “so thrilled” to act as chairwoman for the competition to “make the perfect pudding for the Queen”.

“I hope everyone who enters has lots of fun and I wish them the very best of luck,” she said.

Fortnum & Mason will eventually publish the winning recipe so it can be created by anyone at home. It will be available in time for the Big Jubilee Lunch, taking place on the main bank holiday weekend of the Platinum Jubilee celebrations.

Nadine Dorries, the Culture Secretary, said: “The Platinum Pudding Competition is a wonderful way to celebrate Her Majesty’s 70-year reign and I know it will inspire people of all ages across the UK to get baking.”

Tom Athron, chief executive of Fortnum & Mason, said: “We hope that everyone will roll their sleeves up and get involved, from individuals, families, and community groups to care homes, schools and colleges.

“We can’t wait to see all the inventive entries and share the winning recipe with the nation.”

The competition is open to UK residents aged eight years and older, with a deadline of February 4. For more information, visit www.fortnumandmason.com/platinum-pudding.

All the pomp and ceremony: the itinerary for Platinum Jubilee celebrations

The Queen’s Platinum Jubilee celebrations will include street parties, a pop concert and a pageant, Buckingham Palace has confirmed, as members of the public are invited into the Queen’s private estates to celebrate.

Sandringham and Balmoral will be opened for locals to enjoy screenings of key celebrations, while the Royal Collection Trust stages exhibitions of Her Majesty’s portraits, clothes and jewels at Buckingham Palace, Windsor Castle and the Palace of Holyroodhouse.

The itinerary for the central weekend is today confirmed as:

May 12th to 15th: Platinum Jubilee Celebration