Preheat the oven to 180°C.
Butter an over-proof dish, then butter the bread generously, cut each slice in half diagonally and line the dish.
Sprinkle half the raisins over this layer.
Make a second layer on top, with overlapping slices. Sprinkle over the remaining raisins.
Mix the eggs with the milk, sugar and the nutmeg and pour 3/4 of the mixture over the bread. At this point, leave to soak for at least 30 minutes, a few hours if you can, or even better allow soak over night.
When ready to cook, pour over remaining custard. Place the dish in a roasting tray and pour in enough boiling water to come just over halfway up the side of the dish (basically you are making a bain marie*). The pudding should take about between 45 mins (sometimes an hour, depending on your oven), but check the pudding after around 30 mins to make sure the raisons aren’t burning – if they are, slightly lower the oven temperature.
Last thing to do – warm the apricot jam (or marmalade) gently (!) in a saucepan, then take the dish form the oven and brush the apricot jam over the top of the bread – pop back in the over for around another 5 to 10 minutes.
Serve warm with custard and / or freshly whipped cream.