Sultana Cup of Tea Cake

This was a recipe my mum used to make and it always reminds me of her.
Her 'cup-of-tea-cake' is a fat-less loaf cake that is delicious on its own, or spread with butter. 

Using the same size mug
Put 1 mug caster sugar 
and 1 mug dried sultanas into a large bowl
Pour over 1 mug of hot tea
Leave for at least half an hour, but longer if needed. 
Stir occasionally to make sure the sugar dissolves.

Add 1 beaten egg
2 mugs of self-raising flour

Mix together and pour into a loaf tin
Bake for 1 hour on Gas 4