The expedition was the first to cross Australia from south to north, finding a route across the continent from Melbourne in Victoria to the Gulf of Carpentaria in Queensland.

He was the youngest of six known siblings: King was educated at the Royal Hibernian Military School at Phoenix Park in Dublin between 1847 and 1853, before joining the 70th Regiment on 15 January 1853 at the age of 14.

King obtained his army discharge in Rawalpindi in January 1860 and then travelled to Karachi where he was engaged by Landells to supervise the sepoys who had charge of the camels.

William John Wills was surveyor and astronomical observer and King was appointed as one of the Expedition Assistants on a salary of £120 a year.

Burke split the party again and left on 16 December 1860, placing William Brahe in charge of the depot on Cooper Creek.

Burke, Wills, King and Charley Gray reached the mangroves on the estuary of the Flinders River, near where the town of Normanton now stands, on 9 February 1861.

Already weakened by starvation and exposure, their progress on the return journey was slow and hampered by the tropical monsoon downpours of the wet season.

Burke, Wills and King attempted to reach Mount Hopeless, the furthest extent of settlement in South Australia, which was closer than Menindee, but failed and returned to Cooper Creek.

[citation needed] King was a deeply reluctant celebrity: still physically and emotionally fragile, he struggled to deal with the frenzied public interest in him.

He was not related to his contemporary, surveyor and explorer Stephen King, a participant in John McDouall Stuart's successful 1861–1862 expedition.