In 1818 he married the eldest daughter of Sir Thomas Tyrrwhitt Jones, Bart., of Stanley Hall. By this lady, who died in 1820, he had an only child, Harriet, married in 1841 to Clement, youngest brother of Lord Hill. After his wife's decease, the wayward extravagance which marked the career of John Mytton has probably no parallel. He would not suffer any one to advise him. When heavy liabilities had been incurred, but previously to the disposal of the first property he sold, his agent assured Mr. Mytton that if he would content himself for the following six years with an income of 6,000_l._, the fine old Shrewsbury estate--the earliest patrimony of his ancestors--might be saved; when besought to listen to this warning counsel, "No, no," replied Mytton; "I would not give a straw for life if it was to be passed on 6,000_l._ a year." The result confirmed the agent's apprehensions: the first acre alienated led to the gradual dismemberment of the whole estate; and from this moment may be dated the ruin of the Myttons of Halston. Such was the prodigality of this unfortunate man, that it was said, "If Mytton had had an income of 200,000_l._, he would have been in debt in five years." Most certain it is that, within the last fifteen years of his life, he squandered full half-a-million sterling, and sold timber--"the old oaks of Halston"--to the amount, it is stated, of 80,000_l._
The late Mr. Apperley (Nimrod) wrote a kindly biography of Mytton, illustrated with coloured plates of his strange adventures. One gives a view of Halston, with its glorious plantations, and its noble sheet of water, through which, as the shortest cut, its eccentric owner is riding home. Another illustrates Mytton's "wild duck shooting." "He would sometimes," says Nimrod, "strip to his shirt to follow wild-fowl in hard weather, and once actually laid himself down on the snow to await their arrival at dusk. On one occasion he out-heroded Herod, for he followed some ducks _in puris naturalibus_, and escaped with perfect impunity." The third plate commemorates a practical joke of the frolic-loving squire. One evening the clergyman and doctor, who had dined at Halston, left to return on horseback. Their host having disguised himself in a countryman's frock and hat, succeeded, by riding across the park, in confronting them, and then, in true highwayman voice, he called out, "Stand and deliver!" and before a reply could be given, fired off his pistol, which had of course only a blank cartridge. The affrighted gentlemen, Mytton used to say, never rode half so fast in their lives, as when, with him at their heels, they fled that night to Oswestry.