According to the Daily Mail UK, Guinness, a devout Catholic and an apparently superstitious gentleman, wrote to her:
Last night I heard my bathroom door click open. I was immediately awake and called, “What’s that?”
A very conventional white ghost appeared, an elderly... woman in grey white and heavily veiled.
I couldn’t make out her face. She moved... with dignity down the side of my bed and as I clicked on the light she disappeared.
Guinness's official biographer, Piers Paul Read claims he was not aware of the letter and stated, "Alec was quite superstitious... In the Navy he also had a premonition about being drowned in an oncoming storm. I don’t think he claimed to be psychic but he was open to the idea."
Another "premonition" Guinness had lead him to warn James Dean not to drive on the day the young "Rebel Without a Cause" star died in that fateful car crash in 1955.
Guinness passed away in England on August 5, 2000 at the age of 86.