Our hero next formed a matrimonial alliance with a Miss Poitier, daughter of Colonel Poitier, who had then the command of the military depôt at Kilmainham gaol. This lady being highly accomplished, and possessing a profound knowledge of music, imputed to her husband the secrets of the science, and made him a finished singer. Macklin having the highest opinion of Johnstone's talent, advised him to try the metropolitan boards, and wrote a letter to Mr Thomas Harris, of Covent-garden, who, on the arrival of Johnstone and his wife, immediately engaged them for three years, at a weekly salary of £14, £16, and £18. Johnstone made his first appearance in London on the 3d October, 1783, in his old character of Lionel, and made a complete hit, fully sustaining the ten years' reputation he had acquired on the Dublin stage. After remaining several years at Covent-garden, and finding his voice not improving with time, he formed the admirable policy of taking to Irish parts, which were then but very inadequately filled. His success was beyond example; his native humour, rich brogue, and fine voice for Irish ditties, carried all before him. In fact, he was the only actor who could personate with the utmost effect both the patrician and plebeian Irishman. He next performed at the Haymarket, being one of those who remonstrated with the proprietors of Covent-garden in 1801, against their new regulations. In 1803, he visited his friends in Dublin, where martial law being then in force, on account of Emmett's rebellion, the company performed in the day-time. On his return to London his wife died, and he afterwards married Miss Boulton, the daughter of a wine-merchant, by whom he had Mrs Wallack, who with her children succeeded to the bulk of his large property. In the records of the stage no actor ever approached Johnstone in Irish characters. Sir Lucius O'Trigger, Callaghan O'Brallaghan, Major O'Flaherty, Teague, Tully (the Irish gardener), and Dennis Brulgruddery, were pourtrayed by him in the most exquisite colours. In fact, they stood alone for felicity of nature and original merit.