Mysterious coiled snake revealed in portrait of Queen Elizabeth I

The serpent was depicted being clasped in the Tudor monarch's fingers in the original version of the work – but was painted over at the last minute and replaced with a more decorative bunch of roses.

Deterioration over time has meant the snake has revealed itself once more, its outline now visible on the surface.

The portrait was created by an unknown artist in the 1580s or early 1590s. The image has not been on display at the London gallery since 1921 but it will form part of an exhibition titled Concealed and Revealed: The Changing Faces of Elizabeth I, from March 13 to September 26.

A serpent was sometimes used to reflect wisdom, prudence and reasoned judgment, but the scaly creatures are also linked to notions of Satan and original sin.

The gallery suggested the snake's removal may have been because of the ambiguity.

An artist's impression has been created of what the snake could have looked like, after infra-red technology revealed the changes in the initial design.

A statement from the gallery said: "The snake is mainly black but has greenish blue scales and was almost certainly painted from imagination."

The image of the monarch was painted over a portrait of another woman, whose identity is unknown.

X-ray photography used on the picture showed a female head facing in the opposite direction and in a higher position than the Queen. The eyes and nose of the first face are visible where paint has been lost from Elizabeth's forehead.

The gallery believes the unfinished portrait was by a different painter, showing how 16th century panels were sometimes recycled by artists.