While the oven is preheating prepare the caramel. Add sugar, water and lemon juice to a small saucepan. Cook over high high till it has a light caramel colour. Remove from the hob immediately. distribute caramel among 6 ramekins.
In a small saucepan heat the milk over high heat and add vanilla bean. In a bowl beat eggs and sugar till pale and fluffy. Slowly pour the milk into to the eggs whilst beating constantly. Carefully pour the mixture over the caramel, evenly distributing it among the ramekins.
Heat a baking dish and fill it with water to come up about halfway the sides of the ramekins. Bake in the preheated oven till set but still slightly wobbly, about 40 minutes. Let cool, then refrigerate for at least 8 hours before unmoulding.