Merry Monarch, by Slane out of The Margravine, was foaled in 1842. Bred by Mr. G.W. Gratwicke and trained by John Forth, he won the Derby by a length in 1845, beating Mr A. Johnstone's Annandale, Mr Gully's Old England and Lord Stadbroke's Ida, the favourite, and winner of the Two Thousand Guineas.
Gratwicke, of Ham, near Goodwood in Sussex, inherited a considerable fortune which enabled him to take up racing. Merry Monarch was his second Derby winner; the first being Frederick in 1829, a bay colt by Little John out of a mare by Phantom (who later produced The Magravine, dam of Merry Monarch). Frederick was trained and ridden by John Forth at nearly sixty years of age, making him the oldest man to have ridden a winner of the Derby. It is interesting to note that Forth was evidently still training at the highest level sixteen years later.