Glastonbury is an ancient town, with links to King Arthur that were either reawakened or created by the monks of Glastonbury Abbey in the 12th Century. Rather coincidentally, the Abbey Church had only burnt down a few weeks before King Arthur's grave was discovered...
The town is dominated by the Tor, one of a number of small hills rising sharply from the Somerset Levels, and it is around the base of the Tor that the town has grown up. The Bypass to the west saw the A39 realigned along the former railway line, and as a result the primary A361 was rerouted away from the town centre along existing roads. A possible southern bypass may yet be built!
From 1922 until the mid 1990's, Glastonbury's classified road network barely changed, except for the A369 being renumbered as part of the extended A39 in 1935. After that, the A39 and A361 arrived in the town centre from the north and west respectively, passed down the High Street as one and then merged with the B3151. All three of them then left as a multiplex to head for Street to the South West. However, when the Glastonbury bypass was built, the A39 diverted along it, the B3151 was cut short (although it still continues south of Street) and the A361 rerouted south of the High Street.