In August 1840, Tolmer was part of the punitive expedition to the Coorong after Aborigines massacred 25 shipwreck survivors from the ship Maria, which had been travelling from Port Adelaide to Hobart. He was involved in the 1842 search for Charles Christian Dutton and droving party, believed to have been similarly attacked on their way from Port Lincoln to Adelaide, but no trace was ever found.
After several stints of acting in the position, he was appointed Commissioner of Police on 3 January 1852 replacing George Dashwood. He was instrumental in creating the gold escort route between Mount Alexander near Castlemaine, Victoria and Adelaide in the 1850s (the first arrived in Adelaide on 20 March 1852 with around 600 lb (272 kg) of gold, the second, with 1,620 lb (735 kg) on 4 May 1852; it also carried mail between diggers and their Adelaide families) and also helped to establish the town of Bordertown. In November 1853, following an inquiry into police morale and efficiency, he was demoted to Chief Inspector (Tolmer ascribed the blame to his temporary replacement C. W. Stuart), and six months later he was sidelined to the Public Service.
- Doolette 1997, p. 21.
- "Presentation to Commissioner Hamilton". South Australian Register. Adelaide. 8 July 1881. p. 2 Supplement: Supplement to the South Australian Register. Retrieved 15 August 2014 – via National Library of Australia. 25 years later Tolmer was still bitter.
- "Arrival of the Gold Escort". South Australian Register. Adelaide. 5 May 1852. p. 3. Retrieved 1 March 2012 – via National Library of Australia.
- "Obituary". The Advertiser. Adelaide. 31 October 1928. p. 19. Retrieved 1 February 2016 – via National Library of Australia.