The family vault of the Percy family, dukes of Northumberland, is in St Nicholas's chapel in Westminster Abbey.
A large white marble monument to Elizabeth, Duchess of Northumberland stands in this chapel. This was designed by Robert Adam and sculpted by Nicholas Read. It consists of a basement from which rise two pedestals surmounted by figures of Faith, holding a cross, and Hope, with an anchor, with a wide circular arch between them enclosing a tablet and supporting a sarcophagus. On this is a relief of the Duchess seated on a couch, distributing alms to the poor. Beneath is her motto 'Esperance en Dieu'. The background is a tall pyramid topped by a flaming urn and decorated with an heraldic roundel surmounted by a coronet. On the plinths of the pedestals are a small lion and a unicorn, together with inverted torches, crescents and festoons. The inscription reads:
"Near this place lies interred Elizabeth Percy, Duchess of Northumberland, in her own right Baroness Percy, Lucy, Poynings, Fitz Payne, Bryan & Latimer, sole heiress of Algernon, Duke of Somerset & of the ancient Earls of Northumberland. She inherited all their great & noble qualities, with every amiable & benevolent virtue. By her marriage with Hugh, duke of Northumberland, she had issue Hugh, Earl Percy, Lady F.Eliz. Percy, whose died in 1761, Lord Algernon Percy. Having lived long, an ornament of courts, an honour to her country, & patern to the great, a protectress of the poor, ever distinguished for the most tender affection for her family & friends, she died December 5th 1776 aged sixty, universally beloved, revered, lamented. The Duke of Northumberland, inconsolable for the loss of the best of wives, hath erected this monument to her beloved memory"
Her parents were Algernon, 7th Duke of Somerset and his wife Frances (Thynne). In 1740 she married Hugh Smithson, who later changed his name to Percy, and was 1st Duke of Northumberland. She died at Northumberland House in London. Two of Hugh's illegitimate daughters, Philadelphia and Dorothy, were buried in the south transept of the Abbey. Her son Hugh succeeded as 2nd Duke in 1786 and he married Anne, daughter of John Stuart, 3rd Earl of Bute.
In 1970 a list of those buried in the Northumberland vault were painted on the base of her monument:
"George Seymour, Viscount Beauchamp 1745
Algernon Seymour, 7th Duke of Somerset 1750
Frances, widow of 7th Duke of Somerset 1754
Elizabeth Anne Frances, daughter of the 1st Duke of Northumberland 1761
Elizabeth, Baroness Percy, wife of the 1st Duke of Northumberland 1776
Elizabeth, daughter of Lord Algernon Percy 1779
Charlotte, daughter of Earl Percy 1781
Hugh, 1st Duke of Northumberland 1786
Henry, son of 2nd Duke of Northumberland 1794
Louisa Margaret, daughter of 1st Earl of Beverley 1796
Algernon James, son of Lord Lovaine 1805
Henry Algernon Pitt, son of Lord Lovaine 1809
Margaret, daughter of Lord Lovaine 1810
Isabella Susanna, widow of 1st Earl of Beverley 1812
Hugh, 2nd Duke of Northumberland 1817
Elizabeth, daughter of 2nd Duke of Northumberland 1820
Frances Julia, widow of 2nd Duke of Northumberland 1820
Hugh, 3rd Duke of Northumberland 1847
Agnes, wife of Major General F.T.Buller daughter of 2nd Duke of Northumberland 1856
Algernon, 4th Duke of Northumberland 1865
Charlotte Florentia, widow of 3rd Duke of Northumberland 1866
George, 5th Duke of Northumberland 1867
Henry Hugh Manvers, son of 5th Duke of Northumberland 1877
Louisa, daughter of 5th Duke of Northumberland 1883,
Louisa, wife of 6th Duke of Northumberland 1890
Algernon George, 6th Duke of Northumberland 1899
Alan Ian, 8th Duke of Northumberland 1930
Helen Magdalen, widow of 8th Duke of Northumberland 1965
Hugh, 10th Duke of Northumberland 1988".
The ashes of Elizabeth, widow of the 10th Duke, were interred in December 2012.
Many other members of the family are buried at the family seat, Alnwick Castle in Northumberland.
In this chapel is a simple mural monument by Joseph Nollekens to Isabella and the inscription reads:
"Isabella Susannah, wife of Algernon Percy, Earl of Beverley, died January 24th 1812 aged 61"
Katherine, wife of Henry Percy, Earl of Northumberland, who died on 28 October 1596, was buried in St Paul's chapel. She was the daughter and sole heiress of John Neville, Lord Latimer.
Photos of the monuments can be purchased from Westminster Abbey Library.