For the pancake batter: Mix flour, sugar, salt egg and milk in a bowl until well combined. Set aside.
For the filling: Cut apricots into small pieces. Place in a small saucepan with 300ml (1/2 pt) water. Bring to the boil, cover and simmer for 5 minutes.
Peel, core and slice apples. Add to pan with the apricots, along with lemon zest. Cover and cook gently for 30 minutes. Remove from heat. Pour into sieve over bowl and allow juice to drain. Reserve the juice in the bowl, and return solids to the pan and stir in lemon juice, sugar, cinnamon and nutmeg. Keep warm.
Heat butter or oil in a large frying pan and ladle in some batter. Cook until bubbles appear on the surface. Flip over pancake and cook on the other side until set. Repeat with remaining batter and keep warm.
Fill pancakes with the fruit, roll up and put in an ovenproof dish. Cook in the oven for 10 minutes.
Make juice up to 300ml (1/2 pt) and thicken with custard powder. Serve with pancakes with the sauce and dusted with icing sugar.