Heat oil. Add the onion & garlic & fry for 2 to 3 minutes. Stir in the tomato, bell pepper, chili, ginger, tomato paste, malt vinegar, Worcestershire sauce, stock, sugar & salt.
Bring to a boil, cover & simmer for 30 minutes, removing the lid for the last 10 minutes of cooking. Cool slightly & then puree by forcing through a sieve.
Slice stalks from the corn cobs. Remove the leaves & the silk threads. Place in a pan of boiling, salted water & simmer, covered, for 20 minutes, or until tender (Mark''s note: this seems too long for cooking corn, but the British do like overcooking vegetables!) Drain.
Meanwhile, return the sauce to the pan, bring back to a boil, add sherry & simmer for a couple of minutes. Pour over cobs & serve.