Arnold considers Pope and Dryden to be "prose classics" of the 18th century, rather than poet classics. In terms of poetry, he views Gray's to be the sole 18th-century classic. Gray's reputation as a poet rests primarily on his poems to the memory of King George II. These poems are said to display both elegance and delicacy of sentiment. They also represent an attempt by their author to create something like a royal court laureate position in England at that time. However, many critics view these poems as merely fashionable because they imitated the style of Pope's Poems on Various Subjects much more than that of Dryden's own work. Despite this, they remain popular today among students who study English literature at university. It is estimated that between 1760 and 1800, up to five million copies of poems by John Gray were sold in Britain. This makes him one of the most read poets of all time. His work was so popular that several adaptations were made during his lifetime. One such adaptation was Thomas Arne's song "The World Was Wide Enough for Him", which was originally written for the stage but later used as the theme tune for BBC Radio 4. Another was Henry Purcell's opera Dido, Queen of Carthage, which was based on Virgil's account of the same name.