Julius Caesar seems to have been the first to report meeting Giants in Britain; See De Bello Gallico - Liber VI, C XVI J. A. Thwaites translates his words thus: "They (the British) enclose their victims in wickers of osier and burn them at the tops of giant men." Who were the giant men in question? well, there is some doubt, they might have been great hill-figures like the Cerne Giant or the Long Man of Wilmington, they may alternatively have been some sort of sacrificial green man, or they might have been... Oh well, speculation is useless, but that Albion was indeed the land of Giants, is confirmed.
'Dancing', or 'Pageant' Giants were recorded in Europe by the 14th century. One of the first known in Britain; Christopher the Salisbury Giant; still survives. Once the Giant of the Tailors' Guild, he stands in the Salisbury and South Wiltshire Museum, his exact age is unknown, but there exists a repair bill dated 1570.