Finely grate the zest from one lemon and the orange and place in a medium-sized heatproof bowl.  Add the sugar, eggs and butter.

Halve the lemons and orange then extract the juice using the citrus juicer. Add to the bowl and stir with a wooden spoon to combine.

Place the bowl over a pan of barely simmering water and stir for 15-20 minutes, or until the curd is thick enough to coat the back of the spoon. Do not allow to boil.

Pour into clean, sterilized warm jars and seal. Leave to cool then store in the fridge and use within 2-3 weeks.