The Chapel of our Lady’s Choir or Chantry of Our Lady, was not built until 1483-84 by Chris Willoughby and Robert Dymock. Robert Waterton also left 400 marks for lands and tenements to be purchased to the value of 24 marks yearly for the maintenance of 3 Chaplains celebrating divine service in the chapel and for his soul and that of his wife Cecily.

The chapel is rich with lavish detail. The stonework has been refaced and its details renewed, but the four-light windows, with flattened heads, east and south, and a rectangular doorway between the two south windows are of style contemporary with the erection. A 15th century pointed arch opens from the chancel to the chapel, there is modern walling and a light oak screen in which a narrow door was erected in 1901.

Between the chancel and chapel is a beautiful canopied altar tomb of alabaster bearing the recumbent figures of Robert Waterton and his wife Cecily, their hands together as if in prayer. Robert Waterton is clad in plate armour, his feet resting upon a lion, and his head resting upon his helmet, which bears a plume of feathers. A chain is round his neck and round his waist is a richly-jewelled belt from which hangs a dagger. He has striking facial features and beard. His wife is dressed in a long, loose garment, her richly dressed head resting upon a cushion supported by angels. Two pet dogs wearing bells are at her feet. Both figures wear massive rings. The tomb has five niches with arches. In the south/central is a figure – God the Father – and the arms of the Waterton and Fleming families (Fleming was Cecily’s family).

Opposite, under the window of the south wall of the chapel, is the tomb of Lionel Lord Welles and his wife Cecilia, the daughter of Robert Waterton. That monument is also of alabaster, a fine example of 15th century work. The figure of Lord Welles is clad in armour, his head rests on his helmet, his feet upon a lion (a lion is part of his crest). He has a chain round his neck, a belt with jewels and the garter with its motto on his left leg. Over his armour is a surcoat with the arms of the Welles. On the left of Lord Welles is his wife, her head, with mitred headdress, is richly dressed, resting upon a cushion supported by angels. She wears a mantle embroidered with the arms of the Welles family. At her feet are two small dogs, one asleep, the other pulling his mistress’s mantle with his teeth. The tomb bears the arms of Waterton, Welles and Willoughby families.

Lionel Lord Welles was killed at the Battle of Towton in 1461. His body was brought back to Methley in a sack – a Lancastrian Lord brought back to his allied Lancastrian Methley home. His remains were hidden in a sack to prevent them being mutilated by his enemies.

The Chapel contains other fine monuments to the Savile family. On the north side is a large monument by Peter Scheemakers with effigies of Charles Savile, semi-recumbent, who died 1741, and his wife Aletheia, who died in 1759, seated holding an open book. The arch under which this monument stands was, until 1901, blocked by a wall. The lowest part, until 1938 was protected by iron-spiked railings. In 1938 a light open screen was erected of 3 arches with angels above columns, also a slender waxed oak screen and a narrow door between the chancel and chapel (1938).

On the south wall is a large monument with semi-recumbent figure of John Savile, first Earl of Mexborough (died 1748), by the sculptor Wilton, and erected by his widow. There are murals to other members of the Savile family. Between the tombs of the Watertons and Welles, Dorothy, the third wife of John Savile and widow of Sir Martin Frobisher, is buried. The floor is of chequered marble.

The roof is original 15th century: flat panelled, decorated on its timber framework with armorials (some wrong) and winged angels. The roof subjects were recoloured and gilded in 1954. The inaccurate 18th century paintings of heraldic shields on the roof were continued in later alterations.

The four-light east window contains some very old glass collected from various windows in the church. Some of the glass is 15th century and is akin to that of the same period in York Minster.

The oak altar table, together with cross and candlesticks and kneeling benches, were all designed by Robert Thompson, the “mouse man” of Kilburn, and installed in 1948. The seats bear a “lizard” trademark. Fragments of armour and old banners are displayed. There is a miner’s lamp as sanctuary light over the aumbry.
In October 1987 the Waterton tombs were removed for a major restoration. A nationwide appeal for financial assistance was launched in the 1980s with David Waterton-Anderson, descendant of Robert Waterton, as chairman. The tombs were taken to a Northamptonshire workshop, dried for several months in a controlled atmosphere, cleaned and then treated with a waterproof substance. The total cost was more than £30,000.

One of the first large donations came from the Henry Moore Foundation. The Castleford-born sculptor frequently visited Methley in his youth – he had an aunt living in the village – and he often visited the church and the Waterton Chapel. He is reported to have said that the architecture of St. Oswald’s, especially the corbels in the chancel, aroused his interest in the subject.

The chapel floor, roof, windows and other monuments were also needing repair. The original tiles of the floor round the monuments were reproduced and newly laid.