The South West Tower (Oxford Tower) contains the cathedral's main ring of bells, hung for change ringing in the English style. There are fourteen bells – a ring of twelve with two semitones, which allow for ringing on ten, eight or six bells while still remaining in tune. All of the bells were cast in 1981 by the Whitechapel Bell Foundry from seven bells of the old peal of twelve with new metal added and rehung in a new frame. The length (draught) of the ropes was increased by lowering the floor of the ringing chamber to the level of the south aisle vault at the same time, also allowing for the new bells to be set lower in the belfry than the old, with the intention of reducing stress on the Medieval structure. The heaviest bell (tenor) of this ring weighs . The ringers practise on Thursday at 7:15 pm.