Put the onions and celery into a food
processor and whizz until finely chopped.
Heat the oil in a very large saucepan, add
the onions and celery, cover, then soften
over a low heat for 5 mins. Add the garlic,
cook 5 mins more, then tip in the spices
and cook for 1 min.
Now stir in all remaining ingredients
and bring to the boil. Keep on a bubbling
simmer, uncovered, for 1 hr until the
tomatoes are squashy and the liquid
has reduced by several inches.
Whizz the mix with a stick blender
until smooth, then sieve into a bowl.
The ketchup will thicken a little when
it cools, but if yours seems very runny
(this will depend on the juiciness of your
tomatoes), put it back on the heat and
cook a little longer, stirring often, until
reduced. Keep the ketchup in an
airtight container in the fridge for up
to 3 months, or freeze in batches. If you like, keep in sterilised bottles or jars for up to 6 months - see tip, below.