Preheat the oven to 180°C / 160°C fan / gas mark 4.

In a small saucepan, bring the water to a boil, then add the dates, butter and vanilla. Stir and set aside until lukewarm. When lukewarm, add the date mixture to a mixing bowl. Add the bicarbonate of soda and mix well, then stir in the remaining ingredients until well combined.

Generously butter a traybake tin or baking dish and pour in the cake mixture. Bake for 35 minutes, or until just firm to the touch.

Make the sauce by adding the cream, sugar, treacle, butter and Horlicks to a saucepan. Stir well then whisk on a medium-high heat until the sauce reaches a boil.

Pour half of the sauce over the cooked pudding and keep the remaining sauce to serve separately.