Wash medlars and cut each into four. Peel lemons thinly, squeeze out juice and cut up fine peel. Put medlars, juice and peel into a saucepan, add water and simmer gently until medlars are tender. Sieve and weigh the pulp. Add sugar and spice and return to pan. Stir, bring to the boil, and boil hard for 5 minutes. When it reaches semi-solid consistency, pot and cover in usual way.