As a young midshipman, Mackenzie was obliged to leave the navy when deprived by scarlet fever of hearing and, in part, of speech; but, having learnt to ‘talk with his fingers’, did not allow his disabilities to restrict unduly his social, intellectual and political life.
In December 1783 John Robinson wrote:
As the chief of the Mackenzies, brother and heir of the late Colonel Humberston, is deaf and dumb, it is unlikely he will think of coming into Parliament and therefore it is most likely that Lord Macleod will be elected again.
But Mackenzie did stand and was returned with the assistance of a number of fictitious votes. Listed by William Adam as Opposition, he voted against Pitt’s Irish propositions, 13 May 1785, but did not vote on Richmond’s fortifications plan, 27 Feb. 1786; and although he had intended to be present at the expected division of 4 May 1787 on the Prince of Wales’s debts, was detained in Scotland by his wife’s lying in.
His real interest lay in the improvement of his Scottish estates; but the expense involved in his schemes for building new villages, improving agriculture, and promoting education strained his resources. He was obliged to sell the Humberston estate which he had re-purchased and, as the Seaforth estates were still burdened with £100,000 debt at 5 per cent interest, resolved to reduce his extravagant expenditure in London and restore his finances by living for some five or six years in Lewis.
He died 11 Jan. 1815.
