[1] Foster was born on 21 December 1961 in Pembury, Kent, England, and moved with his family to New Zealand aged 5, originally settling in the Wellington suburbs of Ngaio and Khandallah before becoming a long-term Karori resident.

[5][6] Foster announced his third campaign for the mayoralty at the 2019 local elections and gained endorsement from Sir Peter Jackson.

[10] Foster was the president, and is now a life member, of TRAFINZ, which represents local authority views in New Zealand regarding road safety and traffic management.

[14][15] Significant policies undertaken in his tenure included the funding of the climate change "Te Atakura – First to Zero" action plan and the announcement of preferred options for the Let's get Wellington Moving transport infrastructure package.

This included a second Mount Victoria Tunnel and a mass transit route from the Wellington railway station via the Basin Reserve to Newtown and Island Bay.

[16] In April 2021, local mana whenua iwi Ngati Toa Rangatira and Taranaki Whanui were invited to have a representative with voting rights at council committee meetings.

[18] In July 2021, Foster received acclaim from colleagues typically referenced as his political adversaries for his decision to light up the exterior of the council-owned Michael Fowler Centre with the colours of the transgender flag following confirmation a group considered by some to be transgender-exclusionary would speak there.

[citation needed] In addition, Foster attended a counter-rally with Labour Party councilors Fleur Fitzsimons and Teri O'Neill, draped in the transgender flag.