Heat oven to 180C/160C fan/ gas 4. Put the ham on a wire rack or trivet set over a large roasting tin, pour in 480ml warm water and cover tightly with foil. Put the ham in the oven, immediately reduce the heat to 160C/140C fan/gas 3 and cook for 5 hrs.
Meanwhile, put the maple syrup, apricot jam and brown sugar in a heavy-based pan and stir in 50ml water. Bring to the boil, then remove from the heat and leave to cool.
Take the ham out of the oven. Increase the temperature to 200C/180C fan/gas 6. Open the foil, being careful of the hot steam. Remove the rind from the ham by inserting a sharp knife under it at the opposite end to the knuckle bone, gently lifting it away from the fat (try to keep as much fat on the leg as possible so that it will protect the ham and stop it drying out).
Decorate the ham by scoring the fat with a knife to make large diamond shapes, taking the knife from one corner to the other, then making parallel scores 4cm apart. Repeat in the opposite direction. Put a clove in the corner of each diamond. Brush the ham with the sugar mixture, pushing it into the scores with the brush.
Return the ham to the oven, placing it back on the trivet over the water. Bake for a further 45 mins until deeply coloured. Serve hot or cold. Will keep in the fridge for up to one week.