Cut the tomatoes into quarters. Carefully remove the seeds, placing them in a strainer over a bowl as you clean the tomatoes. Strain as much juice as possible from them and discard the pips. Cut the tomato flesh into neat dice and set aside.
Whisk the vinegar and olive oil into the tomato juice and once emulsified add the tomato dice, garlic, herbs and seasoning. Set aside.
Cook the pasta in boiling salted water with a tablespoon of the vegetable oil. Drain thoroughly and keep warm while you cook the prawns.
Heat the remaining 3 tbsps of vegetable oil in a non stick frying pan. When it is very hot, add the prawns and stir fry until they turn pink.
Toss the tomato vinaigrette and prawns into the pasta and serve hot or cold.