Westminster Abbey

Arguably one of the most recognizable buildings in England, the Collegiate Church of St. Peter at Westminster was founded in the 10th century, possibly earlier. In 1245, Henry III started the construction of the present church.

G.G. Scott designed the altar and reredos that were erected in 1867. The mosaic of The Last Supper is by Salviati based on a cartoon by John R. Clayton, while the sculptures are by Henry Hugh Armstead.
 

An article in The Illustrated London News from 1867.

 The reredos circa 1870-90.

The Salviati reredos today.

Prince William and Kate Middleton got married in front of this altar in April 2011.

Sources:
Wright, John. Some notable altars in the Church of England and the American Episcopal Church. New York: The MacMillan Company, 1908. 74.
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Papers Read at the Royal Institute of British Architects. Session 1868-69. London: Rooms of the Institute. 1869. 45.