H.M.S. Britannia, one of the largest ships of her day, was laid down in 1813 and launched in October 1820. A fine three-decker of 120-guns, she measured about 2,616 tons and carried a crew of 594 officers and men, 66 boys and 160 marines. First commissioned in January 1823, she remained in Plymouth for several years as one of the harbour's guardships and then did some short spells of service in the Mediterranean before becoming flagship at Portsmouth in 1836. After further commissions in the Mediterranean, she returned to Portsmouth in 1850 to become Guardship-of-the-Ordinary and remained there until 1854 when, following the outbreak of the Crimean War, she was sent to the Black Sea as flagship to Vice-Admiral Dundas. Action there included leading the Anglo-French fleet in to bombard Sebastopol on 17th October 1854 but, when peace was concluded, she came home to Portsmouth where she was laid up until recommissioned on 1st January 1859 as the first training ship for naval cadets. Her original moorings in Haslar Creek (Portsmouth) and then Portland proving unsuitable, she was eventually moved to Dartmouth in 1863 where she lay until broken up in 1869. By that time, however, she had so proved her usefulness that she was replaced by a larger vessel, the much newer Prince of Wales of 1860, which was promptly re-christened Britannia in order to maintain the name which had already become synonymous with training boys for a career at sea.