The Fresh Choice wine buyer co-stars as one of the commandants of the prison where Jean Valjean is paroled and the man who goes on to become a recurring presence in the ex-convict's eventful life.
"I give him his parole and Javert appears by coincidence right through Les Miserables," Mr McLay said.
"Because Valjean breaks his parole, Javert makes it his life ambition to make sure he returns to spend a few more years breaking rocks in the hot sun."
The life member of Showbiz Queenstown and committee member for 10 years performed in his first amateur dramatic production as a dancer in The Doo Wop Club in 1992.
Since then, he has performed in more than 30 plays, musical theatre and Shakespeare productions.
His past characters have always had a comedic side - however, Javert was "straight down the line" and the challenge was to make the audience empathise with the man, he said.
Javert's pursuit of Valjean leads to breaking point.
"The law and God are the two driving forces in Javert's life," Mr McLay said.
"He's very similar to Valjean in his background. Javert's mother was a prostitute, his father was a thief and he was born in a jail, but he chose what he believes is the righteous path instead of a life of crime."
The Queenstown resident of 20 years has prepared for his role by learning to constantly stand rigidly straight and training his singing voice for the staccato rhythms of the character.
"I don't claim to be a singer but it's all about the process of rehearsals and being comfortable with the material."
Mr McLay said the excitement was building between cast members as opening night, May 13, approached.
"There are a lot of newcomers coming to the stage at this level as well as experienced [actors].
Hopefully, that's rubbing off and giving them some confidence.
"We're starting to see the company feeling comfortable with their characters. It's going to be a big show for Queenstown and you don't want to miss out on it."
