As many a courtier fatally found out, it was never a good idea to displease the Virgin Queen.

Which may explain why an artist carried out some serious alterations to his first draft portrait of Elizabeth I back in the 16th century.

Where he had drawn the Queen clutching a serpent, the painter had second thoughts and substituted a much more feminine bunch of roses.

Revealed once more: The image of a snake has appeared in a 16th century portrait of Queen Elizabeth I. A faint outline of the coils can be seen superimposed on her hand, while the serpent's body, - seen as dark shading - follows the line of the flowers she is holding and also passes beneath her fingers

What lay beneath: An artist's impression of what the snake may have looked like, left, and an infra-red image of the altered design. A serpent was sometimes used to reflect wisdom but they are also linked to notions of Satan and original sin

The revisions would have remained a mystery had it not been for the ravages of time.

For yesterday, the National Portrait Gallery revealed how the image of the coiled snake had re-appeared.

Deterioration over the centuries has meant the serpent depicted in the Tudor monarch's fingers in the original version has revealed itself once more, with 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 due to the ambiguity of the emblem. An artist's impression has been created of what the snake could have looked like, with infra-red technology revealing 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 covers a portrait of another woman, whose identity is unknown.

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