THIS is the eerie moment when the head turns blue on the effigy of a knight in Hereford Cathedral.

The striking effect happens when sunlight falls through the stained glass of a £1million window dedicated to the SAS Regiment.

Hereford Times Camera Club member Malcolm Hince captured the phenomenon on camera when he was in the cathedral taking pictures.

He said a woman spotted him and directed him towards the knight's tomb.

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"I was just taking some 3D photos of the tomb and wandering around photographing other things when a lady who works at the cathedral came up to me and said, 'Quick, have a look at this. It's really exciting.

"So I followed her over to the tomb and she explained that for only a brief moment each day when the sun shines through the SAS window it turns the knight's head blue, but only the head."

Currently, the light strikes the knight at around 2pm daily, but the time varies as the year progresses.

The effigy is of Sir Richard Pembridge, who died in 1375. Born in 1338 at Bromscroft, Shropshire, he was one of the earliest Knights of the Garter.

He fought alongside the Black Prince at all of Edward III's major victories during the Hundred Years War.

He ordered in his will that his body should be "buried in Hereford Cathedral, between two pillars of freestone before the image of the Virgin Mary on the south side".

A tomb effigy is a sculpted figure on a monument depicting the dead person.

It represents the deceased in a state of "eternal repose", with hands folded in prayer and awaiting resurrection.

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A husband and wife are sometimes depicted lying side by side. An important official or leader may be shown holding his attributes of office or dressed in the formal attire of his official status or social class.

Sir Richard's effigy has been damaged over the years. One leg was replaced with a wooden one in the Civil War, and then with marble in the 19th century.

The Ascension window is 9m high and comprises 3,000 pieces of glass in 40 different colours.

A team of three German glass specialists installed the glass, with the delicate and intricate work taking just four days to complete.

The window was created by the world-renowned sculptor John Maine, and is one of the most significant pieces of new cathedral art in the world.

It marks the historic and modern link between Hereford and the SAS.