St Leonard's Church reflects a number of changes over the past several centuries, but the E apse and W arch survive from the Norman period. The present church consists of a chancel with semi-circular end, a wider nave and a narthex, divided from the nave by an arch. There is also a S porch. William Thornton, prior of Wetheral and later abbot of St Mary’s, York, seems to have been responsible for certain changes to the church in the early 16thc, as his rebus appears on the S buttress of the chancel. In 1703, the church was in a poor condition. In the same report, Bishop Nicolson made mention of a supposed W tower, said to have been removed at some earlier but unknown date. Pennant, in 1772, wrote that the nave of the church had previously been extended at the west end and that at that time there was still ‘a good rounded arch, now filled up’. Some work was carried out on the church in 1807. The nave was rebuilt in 1869 and some stained glass windows put in the apse in the 1870s. A stone-built S porch and narthex were added in 1908. In 2017, the church was made redundant and put up for sale.

The Domesday Book did not cover this part of England. In 1131-2, Henry I confirmed the chapel of ‘Warthwic’ to the abbot and monks of St Mary’s, York, as they held it when Randulph/Ranulf Meshin held Carlisle. The first underlord of Warwick seems to have been called Odard, who is found as a witness to a charter of about 1130-1. It was Randulf Meschines, however, who made the grant to St Mary’s York. In 1133, Athelwold, first bishop of Carlisle, re-confirmed the gift of Warwick chapel. The chapel was subordinate to Wetheral Priory and the first known chaplain of Warwick was called William, who witnessed various charters between 1200 and 1231. In 1541, Henry VIII gave Wetheral Priory to the dean and chapter of Carlisle, and in 1547 the rectories of Wetheral and Warwick were added. The chapter at Carlisle then leased out these churches to Lord William Howard of Naworth, who was obliged to pay for the curate for each parish. The importance of Warwick was partly due to the ford (later bridge) which crossed the Eden River there on the road between Carlisle and Newcastle.

There has been some debate as to whether the W arch is in its original position, or whether it was originally the chancel arch and subsequently moved. Hyde (2010) suggested that the apse and W arch may even have been built in two different building phases. Although, there is no specific evidence for a W tower, it has also been suggested by some in the past. This may, however, be no more than a suppostion based on the present position of the arch. Thurlby and others have compared the decorative features on the W arch to 12thc work on Carlisle Cathedral. The history, along with the comparisons with the cathedral of Carlisle, suggests a likely date in the 2nd quarter of the 12thc.