Prepare jelly according to directions on the packet.
Line a round 20cm cake tin with plastic wrap, then pour jelly mixture into the tin. Refrigerate until firm.
Preheat oven to 180°C (°355F) and grease a round 20cm cake tin.
Prepare cake mix according to directions on the packet, then pour into the prepared tin. Bake in preheated oven for 45 minutes or until a skewer inserted into the centre comes out clean. Remove from oven and set aside to cool completely.
To assemble the trifle, place cooled cake in the base of a 20cm (8 inch) diameter trifle bowl. Generously drizzle with strawberry gin.
Next, carefully turn the set jelly from the cake tin into the trifle bowl on top of cake. Then insert strawberry slices between the bowl and the jelly.
Generously pour custard over the jelly layer.
To prepare the meringue layer, bring sugar and water to a boil in a saucepan over medium heat. Continue to boil until a candy thermometer reaches 115°C (240°F).
In a bowl, beat the egg whites with an electric mixer until soft peaks form. Fold through lemon juice. Reduce mixer speed to low and while continuing to beat, slowly pour the heated sugar mixture into the egg whites. Increase mixer speed and beat until the meringue has cooled and very stiff peaks form, about 20 minutes. Spoon meringue on top of custard. If desired, you can use a kitchen torch to brown the top of the meringue.