Murrell R. Robinson was employed as acting civil engineer of the Cape Colony as early as 1848. From 1853 or earlier to 1859 he held the position of deputy surveyor-general of the colony, while also serving as justice of the peace for Albany. Following the Eighth Frontier War (1850-1853) he laid out Queenstown, founded in February 1853 as the centre of a newly annexed area. A unique feature of the town is the central hexagon, forming the business centre, from which six streets radiate. Robinson planned this lay-out with the defense of the town in mind, the roads allowing rapid access to any point on the periphery of the town and also serving as firing lines. That same year his Memoranda... on the distribution of lands in the divisions of Queen's Town and Victoria was published in Grahamstown in the form of a pamphlet. During the next few years, with his headquarters at Fort Beaufort, he conducted surveys in the border districts in connection with a settlement scheme initiated by the Governor, Sir George Cathcart.
Robinson was an early member of the Literary, Scientific and Medical Society of Grahamstown (founded in July 1855 as the Grahamstown Medico-Chirurgical Society, but renamed in January 1856). In March 1856 he read a paper before the society on roads and railways. Although there were no railways in southern Africa at that time, he thought that railroads might be constructed along the coast, but that engineering and financial difficulties would prevent their extension into the interior. In June that year he was elected joint vice-president of the society and a year later became its president, a position he held for at least two years. He was furthermore one of the first trustees of the society's Albany Museum.
In 1859 Robinson was appointed deputy colonial engineer. By 1862 he was acting colonial engineer and the next year colonial engineer and commissioner of roads for the Cape Colony. By 1869 he was chief inspector of public works and was concerned mainly with road building and maintenance. One of his favoured projects was building a pass over the Outeniqua Mountains to link Mossel Bay and Oudtshoorn. The pass was built by Thomas Bain* during 1867-1869 and was named Robinson Pass in recognition of Robinson's support for the project. By 1874 he was a member of the Table Bay Dock and Breakwater Management Commission. In 1886 he was listed as a pensioner (General directory..., 1886).