The winning trifle was chosen from nearly 5,000 entries.
The trifle, inspired by the 31-year-old copywriter’s grandparents – and the Queen – will become part of British royal food history, following in the footsteps of coronation chicken and Victoria sponge.
To mark the jubilee, Dame Mary and Ms Melvin showed One Show host Alex Jones how to bake the trifle – which consists of lemon curd Swiss roll, St Clement’s jelly, lemon custard, amaretti biscuits, mandarin coulis, fresh whipped cream, candied peel, chocolate shards and crushed amaretti biscuits.
The trifle was crowned on BBC One’s The Jubilee Pudding: 70 Years In The Baking after the judges, including Dame Mary and Monica Galetti, came to a unanimous decision.
Ms Melvin saw off competition from four other bakers who created a passionfruit and thyme frangipane tart, a jubilee bundt cake featuring home-made Dubonnet jam, a rose falooda cake and a “four nations” pudding featuring ingredients from around the UK.
Ms Melvin, from Southport, Merseyside, previously revealed she had only decided to enter the competition because a friend suggested it to her, and called the experience “surreal”.
The One Show is marking the Platinum Jubilee with two special programmes hosted by Jones and Ronan Keating, beginning on June 2.