Her winning dish was announced by the Duchess of Cornwall on the BBC’s The Jubilee Pudding: 70 Years in the Baking.
The Duchess, patron of The Big Jubilee Lunch, hugged Jemma and told her: “Many congratulations.”
She had previously told judges Dame Mary and Masterchef’s Monica Galetti, that their presence in the kitchen must have been “very off-putting” for the amateur bakers, as they tried to create their best versions with the help of Roger Pizey, Fortnum & Mason’s executive pastry chef.
On her win, Miss Melvin said she could not wait to tell her grandmother, adding: “The thought of people recreating my pudding, especially around the Jubilee, is just a total pleasure.”
The trifle is built from layers beginning with a lemon curd Swiss roll on the bottom, followed by St Clement’s jelly, lemon custard, amaretti biscuits, mandarin coulis, fresh whipped cream, candied peel, chocolate shards and crushed amaretti biscuits on top.
Dame Mary, chair of the judges, said: “It’s absolutely wonderful, I think Britain is going to be so delighted and The Queen too.”
Mr Pizey added: “I really think we’ll be making Jemma’s trifle for at least the next 50 to 100 years without a doubt.”
The competition attracted 5,000 entries, from bakers “aged eight to 108”. A shortlist of 50 was judged on the written recipes, before a final five were selected to assemble their dishes in real life.