Ferguson has previously addressed his surprising communication with Rooney, with the future all-time great an unknown youngster when contact was first made.
In ‘Big Dunc: The Upfront Autobiography by Duncan Ferguson, with Henry Winter’, the Toffees icon said: “What got me through the long, lonely nights in Barlinnie was that I must have received 10,000 letters. Incredible. I killed time reading them all. Fans wishing me well and, yes, some expressing rather different sentiments.
"A young boy called Wayne Rooney wrote. He must have been only nine or 10. I wrote him back, without a clue who this passionate football fan would turn out to become. (Apparently, Wayne still has the letter today.)
"Some people sent me books – books about pigeons, books about football, books about breaking out of prison. They sent me a blow-up sex doll, which got confiscated! But the letters I treasured most were from Evertonians like Wayne.
"Looking back now, I still can’t believe the top brass of Everton – my manager Joe Royle, Club Chairman Peter Johnson and Director Clifford Finch – came to see me. It was really nice of them, brave as well. They came into the waiting room at Barlinnie, and it’s like Beirut in there. A total war zone – people bringing drugs, and misery and menace in the air. Having that support from the high-ups at Everton and the fans meant the world."