finely chop onion and celery, crush garlic and put in large saucepan
saute in olive oil on low heat until onion changes colour
grate carrot and add to saucepan
disolve flour and stock cubes in boiling water and add to saucepan
add tomato puree and herbs to saucepan
bring to boil stirring continuously
turn down to low and simmer uncovered for minimum of 30 minutes and up to 2 hours until sauce is desired consistency, stir occasionally so it doesn't stick to the bottom
Notes
can be made with vegetable stock for a vegetarian option