Archdeacon Thomas, in his History of the Parish of Llandrinio published in 1895, suggested that the site of Llandrinio Bridge represented an ancient crossing, and identified a reference to a medieval ferry in a charter of 1309.^[1] The present bridge was built between 1769 and 1775, almost certainly to the designs of John Gwynn.^[a][2] Gwynn, a native of Shrewsbury, designed a number of crossings over the River Severn, including the English Bridge in his home town,^[4] and Atcham Bridge in Shropshire.^[5] He also worked in Oxford, designing the Covered Market^[6] and Magdalen Bridge.^[7]

At the outbreak of World War II, plans were made for the defence of Britain in the event of a German invasion. In the west, a defensive line, Western Command Stop Line No.1, followed the line of the Severn from Tewkesbury to Shrewsbury.^[8] The line crossed the river at Llandrinio, and the bridge was fortified with a pillbox disguised as an agricultural shed and Dragon's teeth tank traps at its northern end.^[9]

The Severn at Llandrinio is susceptible to flooding, which can lead to frequent closure of the bridge.^[10][11][12] In 2015, particularly severe flooding led to fears that the bridge was at risk of collapse.^[13] Subsequent investigations showed that several of the bridge's keystones had been removed by the floodwaters and a major programme of structural repair was required.^[14]

Llandrinio Bridge is constructed of pink sandstone. Three arches span the river at a length of 45 metres.^[15] Scourfield and Haslam, in their Powys volume of the Pevsner Buildings of Wales, describe Llandrinio as a "humped narrow roadway, yet a most graceful line when seen from the [river] bank."^[2] The bridge is a Grade I listed structure and a Scheduled monument.^[16][17]

• Scourfield, Robert; Richard, Haslam (2013). Powys: Montgomeryshire, Radnorshire and Breconshire. The Buildings of Wales. New Haven and London: Yale University Press. ISBN 978-0-300-18508-9. OCLC 935421607.