Soon after the close of the rebellion Mr. Robinson entered the office of the Hon. Christopher Hagerman, a prominent lawyer and legislator of those days, who held important offices in several administrations, and who was subsequently raised to the Bench. After remaining about two years there he had his articles transferred to Mr. James M. Strachan, of the firm of Strachan & Cameron, one of the leading law firms in Toronto. There he remained until the expiration of his articles, when, in Easter Term of 1844, he was called to the Bar of Upper Canada. He does not appear to have been admitted as an attorney and solicitor until Trinity Term, 1869. Immediately after his call to the Bar he began practice in Toronto, where he formed various partnerships, and continued to practise up to the date of his appointment to the position which he now holds.
On the 30th of June, 1847, he married Miss Mary Jane Hagerman, the second daughter of his former principal. He early began to take an active interest in municipal affairs, and in 1851 was elected as Alderman for St. Patrick's Ward, which at that time included the present wards of St. Patrick and St. John. He held the post of Alderman for six consecutive years; was for some time President of the City Council; and in 1857 was elected Mayor. At the next general election he offered himself to the citizens of Toronto as a candidate for a seat in the Legislative Assembly, and was returned conjointly with the late Hon. George Brown. Like all his family connections, he was a Conservative in politics, and yielded a firm support to the Cartier-Macdonald Administration. While in Parliament he was instrumental in procuring the passage of several Acts referring to the Toronto Esplanade and other local improvements. On the 27th of March, 1862, he accepted the office of President of the Council in the Cartier-Macdonald Administration, and held office until the resignation of the Ministry in the month of May following. He has not since been a member of any Administration, but has always been a strenuous supporter of the Conservative side, and has been returned in that interest for his native city no fewer than seven times. At the general election of 1872 he was returned to the House of Commons for the District of Algoma, which he continued thenceforward to represent until the dissolution. At the last general election for the House of Commons, held on the 17th of September, 1878, he was returned for Toronto West by a very large majority (637 votes) over Mr. Thomas Hodgins, the Reform candidate. He continued to represent West Toronto in the Commons until the 30th of June, 1880, when he was appointed to the office of Lieutenant-Governor of Ontario, as successor to the Hon. D. A. Macdonald.