doesn't say the date or name of interviewer that I could see, but anyway...
http://www.geocities.com/SunsetStrip...djginterv.html
Q: When you first saw or heard Elvis Presley, what'd you think?
DG: Absolutely brilliant! I mean, my first, first record I ever bought was "Rock Around The Clock," Bill Haley. The second was "Jailhouse Rock." Elvis, in his very early years, was staggering. He went down hill a little bit...I suppose, under the influence of the good colonel. I don't know what went wrong, but it certainly did.