Various influential friends perceived the genius and promise of the lad, and were anxious to furnish him with the means of studying in the metropolis; but with rare independence he refused all aid, and by careful economy saved a sufficient sum to enable him to leave for London. There he made a lucky hit by a sketch of the younger Kean, which, like his portrait of Scott, was lithographed and published. He entered the Academy schools in 1828, and carried off the highest prizes open to the students.
He also designed illustrations for several of Dickens's Christmas books and other works. Between the years 1830 and 1836 he contributed to Fraser's Magazine, under the pseudonym of Alfred Croquis, a remarkable series of portraits of the literary and other celebrities of the time character studies, etched or lithographed in outline, and touched more or less with the emphasis of the caricaturist, which were afterwards published as the Maclise Portrait Gallery (1871). During the rebuilding of the Houses of Parliament in London in 1834-1850 by Charles Barry, Maclise was commissioned in 1846 to paint murals in the House of Lords on such subjects as Justice and Chivalry.
In 1858 Maclise commenced one of the two great monumental works of his life, The Meeting of Wellington and Blücher, on the walls of Westminster Palace. It was begun in fresco, a process which proved unmanageable. The artist wished to resign the task; but, encouraged by Prince Albert, he studied in Berlin the new method of water-glass painting, and carried out the subject and its companion, The Death of Nelson, in that medium, completing the latter painting in 1864.
The National Gallery of Ireland hangs his vast painting of The Marriage of Strongbow and Aoife (1854). It portrays the marriage of the main Norman conqueror of Ireland to the daughter of his Gaelic ally; see his page.
The intense application which he gave to these great historic works, and various circumstances connected with the commission, had a serious effect on the artist's health. He began to shun the company in which he formerly delighted; his old buoyancy of spirits was gone; and when, in 1865, the presidentship of the Royal Academy was offered to him he declined the honor. He died of acute pneumonia on 25 April 1870.
His works are distinguished by powerful intellectual and imaginative qualities, but most of them are marred by harsh and dull coloring, by metallic hardness of surface and texture, and by frequent touches of the theatrical in the action and attitudes of the figures. His fame rests most securely on his two greatest works at Westminster.
A memoir of Maclise, by his friend WJ O'Driscoll, was published in 1871.