"I spent the first two years being a sponge, taking everything in and saying very little. They were very kind to me because they knew that I'd come from variety shows, big bands and session working; I hadn't come from acting."
Moving from a womanising thief to a loveable rogue, Tarmey gradually discovered Jack's softer side.
"I was very lucky because he changed his character three or four times." Despite their often-volatile relationship, Jack was totally dedicated to Vera.
"There was always big arguments between them but underneath you could see that they loved each other, they just found it hard to say," says Tarmey, who has been married to Ali for nearly 50 years.
Tarmey and his wife are still close to Elizabeth Dawn, who played Vera from 1974 until ill health forced her to resign in 2007.
"We've gone on holidays with Liz and her husband Brian on the QE2 and done theatre stuff," he says.
Having suffered a heart attack in 1976 before he even joined the Street, Tarmey decided to quit after his son Carl was diagnosed with a brain tumour in 2008.
"That aged me 10 years and my health just deteriorated," he admits. "I miss Jack and all my colleagues but I don't miss the work, which could be really hard. You could work five- to six-day weeks and 12- to 16-hour days and if you have a storyline that could go on for five or six weeks."
Tarmey fondly remembers Betty Driver, who played barmaid Betty Williams from 1969 until her death at age 91 last month. "She was in it even longer than I was," he says. "We had her funeral on a Saturday. Betty arranged everything: all the music, the flowers, the church.
"She was like everybody's mum; she was delightful. With some of the scenes we did, we never stopped laughing but that was in the old days when you had time to rehearse. You don't get that now so there's little time for laughing."
* Jack Duckworth & Me is in bookshops now (Simon & Schuster; RRP $26). Coronation Street plays TV One, Thursdays and Fridays at 7.30pm.