Although a pupil of Thomas Harrison, noted for his use of the Classical and particularly "Grecian" architectural style, this is rarely adopted by Penson. An exception is the once impressive Flannel Market (now Regent Centre) of 1832 at Newtown. For Country Houses he favoured a Neo-Jacobean style; as at Vaynor, Llanrhaidr Hall and Hill House, Gwersysllt. He also used this style for the Butcher's Market at Wrexham. For churches he adopted an assertive and non-archaeological version of French Romanesque, although St Davids, Newtown, built in brick and terracotta, is also influenced by the North German Brick Gothic. More particularly he seems to be copying Saint Salvator's Cathedral in Bruges, with buff (rather than the normal red) bricks and has pyramid capping on the pinnacles. Saint Salvator's tower had been remodelled by Robert Dennis Chantrell following a fire in 1838, and this may provide a connection with Penson The design is probably also influenced by Pugin's Roman Catholic St Chad's Cathedral, Birmingham, which is a slightly earlier example of Brick Gothic revival. It is Penson's innovative use of terracotta at Christ Church, Welshpool that is of particular interest. Christ Church (1839–44) was commissioned by the Earl of Powis and is possibly the earliest example of the terracotta revival in Britain. In this church moulded brownish yellow bricks and terracotta were used for the Romanesque arches of the nave and for the apsidal vaulting of the chancel ceiling