The actor, best known for his long-running role as Smithy on The Bill, was cast as PE teacher Jez Diamond earlier this year after Paul Nicholls left the part unexpectedly.
Viewers will see Jez for the first time on Wednesday as he is introduced along with his wife Sian (Jaye Jacobs) and other new recruits at the school.
Walkinshaw told TV Choice of his early moments on set: "I haven't had a 'first day' in nearly 10 years, which is ridiculous for an actor, and I was petrified. The Bill was a real family unit, everyone was tight.
"On my first day on the set of Waterloo Road I was really quiet, but on my second day, the entire cast started taking the mickey out of me.
"They gave me a right roasting in the staff room and I thought, 'This is great - this is exactly what I'm after'. I felt nice and relaxed after that."
Asked to describe his character, he replied: "Jez is a lovable, decent, thoroughly nice bloke. He adores Sian and will drop everything for her - you could say he loves her too much. I don't think Sian's used to being worshipped and it freaks her out!"
Waterloo Road returns on Wednesday at 7.30pm on BBC One.
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