While the Marks films offered in UK porn magazines throughout the 1970s appear to have been softcore .
Marks ' pornographic nature greatly exaggerated by the ads ( a familiar trait of David Sullivan ) , from the early 1970s onwards Marks had begun dabbling in more explicit material .
While the Marks films offered in UK porn magazines throughout the 1970s appear to have been softcore , and their pornographic nature greatly exaggerated by the ads ( a familiar trait of David Sullivan ) , from the early 1970s onwards Marks had begun dabbling in more explicit material .