Whisk the eggs, orange zest, milk and ground cinnamon in a wide shallow dish..
Soak the bread slices in this mixture for 2 minutes a side
While the eggy bread is soaking, bring the orange juice, marmalade and sugar to the boil in a saucepan, then turn down the heat to a fast simmer for 3-4 minutes. If you need to, let this syrup stand while you cook the bread
Heat the butter in a heavy-based frying pan and cook the eggy bread for about 2 minutes a side over a medium heat until golden.
Serve the French toast with some of the amber syrup poured over each slice, and a jug of extra syrup on the side.