Soak the fruit the night before you bake the bun. To a small bowl add the mixed fruit, glacé cherries and Ruby port. Stir the fruit then cover with clingfilm until needed the following day.
Preheat the oven to gas mark 4/350oF/180oC/160oC fan and line a 2lb/900g loaf tin with parchment paper then set the pan aside. To a medium sized bowl, add the flour, salt, cinnamon, nutmeg and mixed spices. Whisk to combine and set aside.
Add the butter to a microwaveable bowl and melt for around 30 seconds or until fully melted. To a mixing bowl, add the melted butter, vegetable oil and sugar then mix until combined. Mix in the egg, honey, black treacle and vanilla extract then pour and mix in the Guinness.
Pour the wet ingredients into the dry ingredients that you set aside earlier and combine until smooth then fold in the soaked fruit with the ruby port. Pour the mixture into the loaf tin and bake for 1 hour - 1 hour 15 minutes or until a skewer coming out clean.
Make the glaze by adding the apricot jam and the water to a small saucepan. Place it on a medium heat and heat until the jam becomes runny then use a pastry brush to brush the top of the bun with the jam.
Place the baking tin on a cooling rack and allow the glazed bun to cool in the tin for 1 hour then remove the bun from the tin and allow to completely cool directly on the cooling rack.