After the completion of the north aisle work started to give the Church transepts. The south transept became the ‘Chancel of St Catherine’ while the north transept became the ‘Chancel of St Margaret of Antioch’. There is a record of a donation being made for the ‘decoration’ of St Margaret's Chapel in 1321 but, judging from the Decorated period detailing of the architecture, the south transept was first to be completed in about 1340. The north transept dates from later in the century after a delay caused by the recession which followed the Black Death.
St Catherine of Alexandria was one of the most popular of th ‘virgin martyrs in the middle ages and in a church with so many chantries it is not surprising to see her name appear. The Chapel was used especially by the weavers and by the cordwainers (shoemakers) for whom she was a patron saint.
The south transept was built slightly smaller than the north transept but the reason for this is unclear. Like the rest of the church, the roofline was raised in the mid C15. Nevertheless some C14 details remain: fine reticulated tracery and an assortment of carved head corbels.
The clerestorey window dates from this later period, but the glass is modern. It depicts Christ's call to St Peter and St Andrew and His instruction to St Peter to ‘feed his lambs’. Its provenance is not known but from its style it seems to be a pair with its counterpart in the north transept.