She claimed, for instance, to have found proof in Italian and Spanish sources that Bristol merchants reached the New World sometime before 1470, and that Cabot didn't die on the 1498 expedition as widely believed, but returned to England in 1500.
"She had made some extraordinary finds, but she ordered in her will the destruction of all her research following her death," said Jones, who founded the Cabot Project research initiative.
That was done in 2005, when the fiercely secretive Ruddock died aged 89. Her unpublished work -- 78 bags of notes, letters, photographs, and microfilms -- ended up in a shredder.
Another of Ruddock's claims was that Cabot was financed by an Italian bank. Following an invitation to visit the deceased historian's house in 2010, Jones and his co-researcher, Margaret Condon, discovered the source of her information -- in the form of a sticky label on an old shoe cupboard: "The Bardi firm of London" (an Italian bank).
"The Bardi firm of London -- that was all we needed to work out the identity of the Italian banking house that Ruddock kept secret for almost half a century," Jones said.