Phillip Montgomery of Northern Ireland (rathcoole@bytes.org) on 14 March 1997 writes:
"On 12/3/1997 I was watching Hale Bopp at 22:10 GMT and saw a veryt bright object suddenly appear below the comet's tail. I tracked it for about 1 minute and it moved North-Northeast towards the horizon near magnitude 0.0."
Satellites that move this fast are usually seen only very soon after sunset during twilight. I was probably a plane would be my best guess.