Yul Brynner's son, Rock Brynner, appears uncredited as a drunkard. The movie was filmed outside of Dublin, and the young Brynner was studying in Trinity College at the time. Whenever his dad would come to visit him, Dublin's press photographers would have a field day.
This uses many of the same locations as John Huston's O Irresistível Bandoleiro (1969) which was filmed in Ireland around this time.
Jodie Foster planned to make a similar tale featuring John Malkovich as Jonathan Wild in the early '90s for Working Title, but it never came to fruition.
"Jack" says he's 'about 20 years old'. Tommy Steele was around 32 at the time of filming.