Beat eggs with a whisk, then add all other ingredients. Put in a double saucepan. Cook over low heat until it thickens. Stir constantly. Don't boil! Sometimes it takes only 15 minutes to get to the right stage, sometimes 45 minutes. Don't fret about it too much - it normally thickens on standing anyway.

You can do it in a normal saucepan if you don't have a double one. Just use very low heat. You might get little white flecks in the lemon curd but that's ok.