Blenkinsop was born in 1822 in Penryn, Cornwall, England and entered the service of the Hudson's Bay Company in 1840 as a steward. He was sent to the Columbia district, where he served as postmaster at Stikine between 1843 and 1849. In 1846, he married Helen, daughter of Captain William McNeill. When Stikine was dismantled in 1849 he was relocated to northern Vancouver Island where he took part in the construction of Fort Rupert adjacent to the site where deposits of coal had been discovered. It seems he was simply passing through Fort Victoria in March of 1850 when Finlayson noted his presence. As 'clerk in charge' at Fort Rupert in the summer of 1850, he became embroiled in a complex set of disputes which initially involved disgruntled coal-miners, but soon expanded to include mutinous seamen as well as several native communities in the region. In the words of Dr. J. S. Helmcken, who Governor Blanshard appointed to quell the situation; "every man now had a grievance." Events, beyond the ability of Blenkinsop and Helmcken to manage, culminated in the deaths of three Hudson's Bay Company deserters (Charles Lobb, Fred Watkins and George Wishart) and the destruction a native village. Vengeful repercussions in the following year resulted in the deaths of four Nahwitti natives and the destruction of a second village by a force of sixty men aboard HMS Daedalus. Upon the conclusion of the chaotic events in 1851, Blenkinsop turned his attention to overseeing the Company’s coal mining operations as well as other projects such as the production of shingles. Promoted to the rank of Chief Trader in 1855 Blenkinsop left for Fort Colvile in 1856 and then brought his HBC career to an end with a final move to Fort Langley in 1860 where he retired the following year.
During his retirement Blenkinsop took on a number of entrepreneurial jobs as a merchant, farmer, labourer, translator and guide. Largely unsuccessful, he subsequently attained various public offices, including a membership on the joint commission on Indian land in BC which formed in 1876. He was assigned as Indian agent for the “Kwahkewlth agency” in 1881 where he took action to protect Native land and fishing rights, though he simultaneously sought to outlaw the potlatch and promote assimilation. He died at Fort Rupert on June 2, 1904.