I don't have a record of whose tomb it is, but it is obviously old!
As you can see from the back wall and the column, the picture is straight, but obviously the floor has sunk at one end.
Wikipedia tells me (via Philine):
"Around 1333 the Gothic funerary chapel of João Gordo was added. João was a Knight Hospitaller who worked for King Dinis I. His tomb is decorated with his recumbent figure and reliefs of the Apostles." (Wikipedia)
The video is there simply because I like it :-)
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