He built his success and wealth in the advertising business in Australia in the 1970s and 1980s, and later also had diverse investment interests in radio broadcasting, publishing and thoroughbred breeding and racing.

In 1968 together with his Art Director partner Dunc McAllan, he started his own agency in Sydney and the pair soon teamed-up with Rob Palmer and Mike Strauss who had an existing small Melbourne shop with media buying accreditation to start Singleton, Palmer and Strauss, McAllan (SPASM) which opened with offices in Sydney and Melbourne.

[1] SPASM's clients were largely local Sydney retailers and rather than using polished voices, Singleton's ads embraced the tone of working-class man.

Working for a large multi-national with overseas owners was a challenge for Singleton and he left the business in 1977, triggering a long non-compete provision in his contract.

Singleton developed close ties with the Australian Labor Party and created the advertising for Bob Hawke's successful 1987 election campaign.

He has been married to Margaret Wall, Maggie Eckardt, Belinda Green, Liz Hayes, Jennifer Murrant - de facto, Julie Martin,[13] and Sarah Warry.