Spanish ensign captured with their warship, 'San Ildefonso', 74 guns (probably mounting 80 in battle), by the 'Defence' at Trafalgar (see PAD5735). It was hung in the crossing of St Paul's Cathedral during Nelson's funeral service on 9 January 1806 (see PAH7332) and was presented to Greenwich Hospital for display in the former Royal Naval Museum in the Royal Naval College at Greenwich by the Dean and Chapter of St Paul's in 1907. It passed to the NMM with much of the rest of that collection in 1936. This design of ensign was in use from 1785 to 1931. The field is divided into three horizontal stripes; red, yellow, red. On an applied patch in the central stripe is an oval containing the arms of Castile (a yellow/gold castle on a red field) and Leon (a white field with a red lion rampant ), a crown above. The arms appear to have been printed or stencilled. Inscribed on the hoist in ink: 'SAN ELDEFONSO'.

The flag is of wool bunting, woven 29 threads to the inch (warp), 28 threads to the inch (weft) and made of 21 x 405 mm-wide breadths, hand-sewn horizontally with overstitched seams. There is a narrower band of fabric at the top and bottom edge. There are some rectangular holes apparently cut by souvenir hunters at the hoist end and neat patches indicating repairs nearly contemporary with the date of manufacture. The rope hoist is frapped in a linen binding sleeve, stitched to the body of the flag. In 1962 this ensign was suspended for photography from the parapet of the Queen's House, Greenwich - producing an instructive though not now repeatable demonstration of the great size of these flags: this one is 32 feet long, English measure (NMM neg. A3391). A very similar ensign, worn by the 'San Juan Nepomuceno' during the Battle of Trafalgar, is in the Museo de Ejército, Madrid.