Michael Kitchen played Billy with some finely judged deliberate accent slippage.
"Usually I only play Billy for 32 minutes, and he was absolutely exhausted," Pitino added.
Steen continued to play Billy throughout the two series.
Michael Hayden played Billy not as a large, gruff man, but as a frustrated smaller one, a time bomb waiting to explode.
Playing Billy in the curtain-raiser was young Charlie Chaplin.
Also in 1990, he played Billy in the film Blind Fury.
That Michael Hayden, who plays Billy, comes across as a boy in a man's part is no doubt intentional.
John Mills also plays Billy in the film.
Kristofferson was 36 when the film was made, playing 21-year-old Billy.
The choice of the actor to play Billy was "absolutely critical" to the film, he said.