Put the quince and lemon peel and juice in a large, deep saucepan. Cover with water (you'll need about 3.2 litres) and bring to the boil. Reduce to a simmer and cook for 1 hr 30 mins until the quince is very soft.

Line a colander with muslin cloth, and put over a very large saucepan or heatproof bowl. Tip the quince into the lined colander, cover with a clean tea towel and leave to strain for 4-8 hrs until all the juice has dripped out. Discard the pulp, then measure out the strained juice and transfer to a large, deep saucepan (the jelly will bubble up high as it cooks). Add 500g sugar for every 600ml juice.

Bring to the boil over a low heat, stirring to dissolve the sugar. Bring to a rapid bubble and cook until the temperature reaches 105C on a sugar thermometer. Remove from the heat and stir in the orange blossom water, if using. Ladle into hot sterilised jars and seal. Will keep in a cool, dark place for up to a year.