This nightmare seldom happens in London restaurants today - but I guess most vegetarians have lived through it once or twice (at least). Picture the scene: a meal with friends at a well-respected restaurant. The time to order arrives; waiter, pencil and pad poised, grins, and ... oh God! That gutwrenching moment dawns when you see there's no vegetarian main course on the menu (or if there is, it's some sort of basic cheese bake).