You will need a tall jar - the length of your cucumbers, as it were ( settle down, this isn't a Frankie Howerd sketch).
I found the 3 litre Le Parfait is ideal - let's face it, they have to be ideal for something!
Day 1. Take a V shape out of each cucumber without cutting through to the other side. Run a teaspoon down the cucumber and the cut-out to take away the seeds and the pulp.
The stuffing is made by whizzing together in a processor:-
Small jar of capers, drained well
6 large shallots, peeled and roughly chopped
2 cloves of garlic, peeled and roughly chopped
1 red chilli, seeds in or out, just as you like
2 teaspoons yellow mustard seeds
small grating of nutmeg
You will also need some fine string - around 1 metre per cucumber
1-1.5ltrs/3 pints distilled malt vinegar, or cider vinegar
Take one length of your string and tie around one end of the cucumber - fairly firmly - but be careful not to squash the flesh. Continue down the cucumber either winding the string around, or tie it at intervals.