Cut the tomatoes into quarters, place them in a preserving-pan with the salt and vinegar and simmer until the tomatoes are quite soft and broken up. Strain the mixture through coarse muslin or a nylon sieve, then return the purée to the preserving-pan and add the sugar. Continue to simmer till the ketchup starts to thicken, and then add the spices a little at a time, stirring thoroughly until the flavour is to taste.
When the ketchup is reasonably thick, fill into hot bottles and seal immediately, or allow it to cool slightly, then fill the bottles and sterilize at 170° F. for 30 min.
Remember it will be thicker when cold than hot, so don’t reduce it too far.