You don't need pectin sugar for Damsons and you don't need lemon unless you want to add a lemon flavour.
Simmer the damson whole. Leave to cool and then I put on a pair of food grade plastic gloves and squidge through the mixture and remove all the stones. The damsons are quicker to soften if you freeze them first.
Don't worry if you miss any stones as when you are boiling to a set, any stones that you missed will rise to the top.
I will give my basic recipe with the variations in case you fancy something other than plain Damson.
5lb damsons
6lb sugar
1 and 1/2 pints water
1 teaspoon of sunflower oil to be added with the sugar.
The variations are.. for a mulled damson cook the damsons in 1 pint red wine, 1/2 pint water and put 16 allspice berries, 8 cloves, 40g cinnamon stick and 1 tab of whole star anise in a spice ball or muslin, and the juice and rind of 3 oranges, the rind of 2 lemons and the juice of 2.
You can also put 2 teaspoons of brandy in each jar before you pour in the jam.
For Port and lemon damson, add the rind and juice of 3 or 4 lemons depending on the size, and add 2 teaspoons of port to the jars before potting the jam. Did this because we have a glut of port
No one knows what to by MR BEE for special times and he did say once that he liked port. We now have a port lake.
orange and cinnamon is the other one. Add a large cinnamon stick and the rind and juice of 4 oranges.
You can add 2 teaspoons of brandy to the jam jars if you want as well.
These make unusual jams as presents for the winter festival.
I have been buying the smallest preserving jars from the Swedish store, 80p each and filling them with preserves to give as gifts. I was a bit concerned that you couldn't but replacement rubber seals for them but I find that the kilner jar replacement rings fit.