A free-standing bell tower seems to have existed until the early 15th century, further to the west. The present, leaning west tower was built in stages, and completed between 1441 and 1460. The highest stage is at a different angle to the vertical to the lower stages, as the masons attempted to correct for the subsidence of the lower stages. The top of the tower leans from the vertical. It is high. The lean is popularly attributed to the foundations of the tower being built on top of wool-sacks but is most likely due to the soft alluvial clay underneath being compressed.