Shelley, born the heir to rich estates and the son of an Member of Parliament, went to University College, Oxford in 1810, but in March of the following year he and a friend, Thomas Jefferson Hogg, were both expelled for the suspected authorship of a pamphlet entitled The Necessity of Atheism.

In 1811 he met and eloped to Edinburgh with Harriet Westbrook and, one year later, went with her and her older sister first to Dublin, then to Devon and North Wales, where they stayed for six months into 1813. However, by 1814, and with the birth of two children, their marriage had collapsed and Shelley eloped once again, this time with Mary Godwin.

Along with Mary's step-sister, the couple travelled to France, Switzerland and Germany before returning to London where he took a house with Mary on the edge of Great Windsor Park and wrote Alastor (1816), the poem that first brought him fame.

In 1816 Shelley spent the summer on Lake Geneva with Byron and Mary who had begun work on her Frankenstein. In the autumn of that year Harriet drowned herself in the Serpentine in Hyde Park and Shelley then married Mary and settled with her, in 1817, at Great Marlow, on the Thames. They later travelled to Italy, where Shelley wrote the sonnet Ozymandias (written 1818) and translated Plato's Symposium from the Greek. Shelley himself drowned in a sailing accident in 1822. (poemhunter.com)