Of all the events which use sport as an excuse to ease out the champagne corks and have a social junket-Ascot, Wimbledon, Lord's, Cowes - the most exquisitely English is Henley Royal Regatta. The course is English to the point of idiosyncrasy: it doesn'conform to international standards for one inch of its beautiful length. Yet every oarsman in the world wants to row on it. Even the Russians send their best men to heave and sweat past the Stewards' enclosure, where the English upper classes relax in deck-chairs, wear dazzling boat-club blazers and caps, sip punch and champagne, gossip, and clap politely.