Elizabeth Taylor once accidentally left the 33.29-carat Krupp Diamond in a hotel suite

Mendelson - who worked for her from 1990 until her death and is co=trustee of her estate - told PEOPLE magazine: "This was my first trip with her abroad and I'd never been out of the country before. I met her in Gstaad but we were going to Venice.

"We stayed at the Cipriani, and she had a huge suite there. She was married to Larry [Fortensky] at the time. There were some AIDS events and we went to a luncheon.

"I was sitting at the table next to her. She was sitting next to the artist, Robert Rauschenberg, and she tapped me on the shoulder. She said, 'Come close.' And she whispered my ear, 'I left the Krupp Diamond.' "

Taylor wore the Krupp Diamond - originally named after the family of German industrialists - as a ring, and described it as her favourite piece.

Mendelson recalled: "She always traveled with not all her jewelry, it was too much, but she wasn't shy about traveling with her jewels, like Cartier and the Bulgari, and these historic pieces.

"She said, 'Don't tell anyone. Take Moshe,' who was her head of security at the time. We went in a speedboat back to the hotel.

"I walked into the suite and we had told them they could clean. So there was this whole cleaning crew in this massive suite and people were vacuuming and all this stuff."

He can still remembered seeing the jewel - which was renamed The Elizabeth Taylor Diamond after her death - "just sitting there" on the side in the bathroom, and it appeared the staff had "cleaned right around it".

He said: "In the bathroom, the diamond is just sitting there. I grabbed it and put it in my pocket and went back to give it to her...

"It's so crazy, but I think she was protected. She had such an amazing spirit and such courage, but she was protected."