THE long arm of Hongkong reaches everywhere - and now even to popular American talk show host David Letterman's new show for CBS. TV giant CBS has just bought New York's historic Ed Sullivan Theatre to serve as the studio for Letterman - who switched from NBC in a deal worth millions - when he starts his new late-night show in the summer. Sealing the deal was the property company Winthrop, which opened its Asian operation in Hongkong just over a year ago. In fact, hardly was the ink dry on the theatre deal than Winthrop's Asia managing director, Jeffrey Furber, was off to the States to scout for property on behalf of local investors. The Ed Sullivan Theatre was also where Elvis Presley and The Beatles made celebrated appearances. So, if we really want to stretch a point, we can also now claim that Hongkong played a part in the success of John, Paul, George and Ringo. We'll pass on Elvis and Ed Sullivan.