London's ever-more-discerning wine drinkers are homing in on Chile's remarkably delicious, affordable, fruit-packed wines of every hue. You've tried their Merlots, you've tried their Chardonnays and Sauvignons. We know the grapes well, or at least we thought we did. But what about this 'new' grape variety called Carmen?re, of which Chile is absolutely stuffed full and which is now making a strong appearance over here?