through the North Downs, they constitute the most southeasterly group of megalithic monuments in the British Isles, and the only megalithic group in eastern England. The archaeologists Brian Philp and Mike Dutto deemed the Medway Megaliths to be "some of the most interesting and well known" archaeological sites in Kent, while the archaeologist Paul Ashbee described them as "the most grandiose and impressive structures of their kind in southern England". The Medway Megaliths can be divided into two separate clusters: one to the west of the River Medway and the other on Blue Bell Hill to the east, between apart. The western group includes Coldrum Long Barrow, Addington Long Barrow, and the Chestnuts Long Barrow. The eastern group consists of Smythe's Megalith, Kit's Coty House, Little Kit's Coty House, and several other stones that might have once been parts of chambered tombs, most notably the White Horse Stone. It is not known if they were all built at the same time, and it is not known if they each served the same function or whether there was a hierarchy in their usage. The Medway long barrows all conformed to the same general design plan, and are all aligned on an east to west axis. Each had a stone chamber at the eastern end of the mound, and they each probably had a stone facade flanking the entrance. They had internal heights of up to , making them taller than most other chambered long barrows in Britain. The chambers were constructed from sarsen sandstone, a dense, hard, and durable stone that occurs naturally throughout Kent, having formed out of sand from the Eocene epoch. Early Neolithic builders would have selected blocks from the local area, and then transported them to the site of the monument to be erected. These common architectural features among the Medway Megaliths indicate a strong regional cohesion with no direct parallels elsewhere in the British Isles. Nevertheless, as with other regional groupings of Early Neolithic long barrows—such as the Cotswold-Severn group in south-western Britain—there are also various idiosyncrasies in the different monuments, such as Coldrum's rectilinear shape, the Chestnut Long Barrow's facade, and the long, thin mounds at Addington and Kit's Coty. These variations might have been caused by the tombs being altered and adapted over the course of their use; in this scenario, the monuments would be composite structures. The builders of these monuments were probably