It may be a long time before Sir Benjamin Slade lends anything more from his prized collection for public display around his Somerset, England, home. Sir Benjamin paid $75,000 or so at auction for a rare 1909 Steiff teddy bear from the estate of Elvis Presley. (You may remember, one of the King's hit songs was "(Let Me Be Your) Teddy Bear.") Somewhat later, the proud new owner of "Mabel" was talked into allowing a local tourist attraction, Wookey Hole Caves, to make it the centerpiece of an exhibit of 1,000 teddies designed to appeal to children. But their combined value was so great that insurers insisted the display be guarded by trained dogs . One of them: Barney, a sturdy Doberman with six years' experience. All was going well until one night last week, when something in Barney snapped. Within minutes of beginning his shift, he went on a rampage that resulted in arms, legs, and stuffing being strewn all over the floor. Alas, "Mabel" was among the most badly battered. Why? Perhaps because of "a rogue scent" that the dog objected to. Sir Benjamin was "hopping mad" at the news, reports say. As for Barney, his career is over. Wookey Hole Caves doesn't want him back, so he's being retired to a farm.