His career expanded in the mid-1970s after meeting Marty Johnstone, who at this stage was doing financially well importing cannabis "buddha sticks" into New Zealand from Southeast Asia.

Clark and Johnstone, wanting to expand their market and money, started importing high quality white heroin into both New Zealand and Australia.

[7] Clark was ruthless as controller of his operations and killed a number of associates including Gregory Ollard, a Mr Asia drug supplier and heroin addict.

After his divorce from Sally, Clark entered into a relationship with heroin addict Norma Fleet, whom he married in Wi Tako Prison.

[13] In October 1979, Clark had Marty Johnstone (Mr Asia) lured to Britain on the pretext of a drug deal to take place in Scotland.

Johnstone was murdered by his longtime friend Andy Maher under the orders of Clark, and his handless body was dumped in Eccleston Delph, Lancashire, mutilated in a hasty but failed attempt to foil identification by the police.

[15] Clark was played by Philip Quast in the episode "All Good Friends" in the 1992 British ITV series Crime Story dealing with the killing of Marty Johnstone.