In 1803, Campbell resolved to settle in London; in his progress to the metropolis he visited his friends Roscoe and Currie, at Liverpool. On the 10th September, 1803, he espoused his fair cousin, Matilda Sinclair, and established his residence in Upper Eaton Street, Pimlico. In the following year, he sought refuge from the noise of the busy world in London, by renting a house at Sydenham. His reputation readily secured him a sufficiency of literary employment; he translated for the _Star_, with a salary of two hundred pounds per annum, and became a contributor to the _Philosophical Magazine_. He declined the offer of the Regent's chair in the University of Wilna, in Russian-Poland; but shortly after had conferred on him, by the premier, Charles Fox, a civil-list pension of two hundred pounds. In 1809, he published his poem, "Gertrude of Wyoming," along with the "Battle of the Baltic," the "Mariners of England," "Hohenlinden," "Glenara," and others of his best lyrics. This volume was well received, and added largely to his laurels. In 1811, he delivered five lectures on poetry, in the Royal Institution.
Campbell was now a visitor in the first literary circles, and was welcomed at the tables of persons of opulence. From the commencement of his residence in London, he had known John Kemble, and his accomplished sister, Mrs Siddons. He became intimate with Lord Byron and Thomas Moore; and had the honour of frequent invitations to the residence of the Princess of Wales, at Blackheath. In 1814, he visited Paris, where he was introduced to the Duke of Wellington; dined with Humboldt and Schlegel, and met his former friend and correspondent, Madame de Staël. A proposal of Sir Walter Scott, in 1816, to secure him a chair in the University of Edinburgh, was not attended with success. The "Specimens of the British Poets," a work he had undertaken for Mr Murray, appeared in 1819. In 1820, he accepted the editorship of the _New Monthly Magazine_, with a salary of six hundred pounds per annum. A second visit to Germany, which he accomplished immediately after the commencement of his editorial duties, suggested to him the idea of the London University; and this scheme, warmly supported by his literary friends, and advocated by Lord Brougham, led in 1825 to the establishment of the institution. In the year subsequent to this happy consummation of his exertions on behalf of learning in the south, he received intelligence of his having been elected Lord Rector of the University of Glasgow. This honour was the most valued of his life; it was afterwards enhanced by his re-election to office for the third time,--a rare occurrence in the history of the College.