For many years, Shacklock was a trustee of the Dunedin Savings Bank, including a term as chairman.

[5] Shacklock entered local politics in 1899, when he was elected as a member of the South Dunedin Borough Council.

[6][7] Subsequently, Shacklock served as a Dunedin city councillor until 1913, when he did not seek re-election to council but stood as a mayoral candidate only, finishing in third place.

[9] He did not contest the mayoralty at the 1915 municipal elections, but was returned as a city councillor, remaining in that role until 1935, when he chose not to stand for re-election.

[5] Shacklock was an officeholder for the Cargill Road Methodist Church for over 50 years, and was a member of the Hand and Heart Lodge, Independent Order of Oddfellows Manchester Unity.