John Leland writing sometime between 1536 and 1539 states that the fairest of the toun is al yn one streate.  Maps and early surveys make clear that this one street is the present High Street, leading from the bridge (on the site of the present Town Bridge) and up the road now called Stow Hill, and then to the south side of St Woolos Church. A clue to the antiquity of Stow Hill may be that it is now a partly sunken road with raised pavements. The main town was partly protected by marshes to the north and south, by the river Usk to the east, and possibly by defensive structures to the west.
In the Middle Ages the road route across South Wales leading from Chepstow to Cardiff would cross over Newport Bridge through the town and past St Woolos Church (now the cathedral). To the west of St Woolos this road branched, with the south branch descending on to the Wentloog Levels going towards Cardiff, and the north branch going towards Bassaleg and Caerphilly.
Newport was therefore a convenient location for markets and fairs, and for the collection of rents and tolls associated with them. The income derived from these rents and tolls was no doubt the reason for the lord granting the privileges enjoyed by the burgesses. The market place was in the present High Street and this road still widens out in the vicinity of the Murenger House. In the seventeenth and eighteenth centuries a market house stood in the middle of the road.
A survey of rents in 1570 is particularly useful in identifying where streets and properties were located.  Modern road names can still be identified. Apart from the High Street they include Corn Street (formerly Cornes lane but now this street is on a slightly different alignment), Skinner Street (formerly Skynners lane), and a lane leading to Baneswell (formerly Paynes well).
The 1750 map also shows that, on the east side of High Street, Griffin Street (then Griffin Lane), Market Street (then called Cross Keys Lane) and what is now the Carpenters Arms Lane (but was once known as St Lawrence’s Lane) were in existence in the eighteenth century. These are all likely to be medieval in origin. On the west side of High Street a road called (St.) Thomas Street was in existence until the twentieth century. This led to the original Mill Street, which in turn led to a water mill close to the river. A road (including the later Pentonville) headed from the west from Bassaleg via Ridgeway, in the direction of the bridge. It would have joined the middle of Thomas Street where Thomas Street widened out. This Bassaleg/Ridgeway road may predate the later medieval castle and street layout, which obstruct a direct line to the bridge.
The town was split in two by the Town Pill. This pill went from the River Usk a little way south of the castle and bridge, following a line between Skinner Street and Griffin Street at least as far as the High Street where there may have been a bridge over the pill. The area to the north of the pill as far as the castle was called the Great Bailey, and the area to the south of the pill as far as the present Riverfront theatre (where the Newport Ship was discovered) was called the Small Bailey.
How far you can call Newport a planned town is debateable, since it straddles a main thoroughfare that must have come about after the construction of the bridge, and may just have evolved over a period of time. However its significance as a market town appears to have developed early on, and there may well have been inducements to new settlers by the Norman lords of Gwynllŵg.
1. Toulmin Smith, L., (editor) The Itinerary in Wales of John Leland in or about the years 1536-1539. (London 1906) 14
2. ‘Survey of the rents due to the earl of Pembroke 13 September 1570’. National Library of Wales Mss 17008Dpublished in Bradney, J.A., (Gray, M, editor) A History of Monmouthshire Volume 5 The Hundred of Newport (Cardiff & Aberystwyth 1993) 32-35
Bob Trett 2010