New South Wales to sail for Europe, when, in 1792 they accompanied Governor Phillip to England and were presented to King George III. In 1813, Gregory Blaxland, William Lawson and William Wentworth succeeded in crossing west of Sydney and over the formidable barrier of forested gulleys and sheer cliffs presented by Colomatta, a mountain range on Gundungurra & Dharug Country later named the Blue Mountains, by following the ridges instead of looking for a route through the valleys. At Mount Blaxland they looked out over "enough grass to support the stock of the colony for thirty years", and expansion of the British settlement into the interior could begin. In 1820, British settlement was largely confined to a 100 kilometre radius around Sydney and to the central plain of Van Diemen's land. The settler population was 26,000 on the mainland and 6,000 in Van Diemen's Land. In 1824 the Governor Sir Thomas Brisbane, commissioned Hamilton Hume and former Royal Navy Captain William Hovell to lead an expedition to find new grazing land in the south of the colony, and also to find an answer to the mystery of where New South Wales's western rivers flowed. Over 16 weeks in 1824–25, Hume and Hovell journeyed to the bay Naarm on the land of the Kulin nation, later named Port Phillip, and back. They found many important sites including the Murray River (which they named the Hume), many of its tributaries, and good agricultural and grazing lands between Gunning, New South Wales and Corio Bay, Victoria. Charles Sturt led an expedition along the Macquarie River in 1828 and found the Darling River. A theory had developed that the inland rivers of New South Wales were draining into an inland sea. Leading a second expedition in 1829, Sturt followed the Murrumbidgee River into a 'broad and noble river', the Murray River, which he named after Sir George Murray, secretary of state for the colonies. His party then followed this river to its junction with the Darling River, facing two threatening encounters with local Aboriginal people along the way. Sturt continued downriver on to Lake Alexandrina, where the Murray meets the sea in South Australia. Suffering greatly, the party had to then row back upstream hundreds of kilometres for the return journey. Surveyor General Sir Thomas Mitchell conducted a series of expeditions from the 1830s to 'fill in the gaps' left by these previous expeditions.