Reports of ghostly apparitions of Henry VIII's fifth wife Catherine Howard have echoed round the corridors of the palace for the last century.

Royal historians believe the myth was invented after the palace opened its doors to the public in 1838 but that does not explain reports of paranormal activity experienced by visitors in the Haunted Gallery.

Two women taken on separate guided tours fainted at exactly the same spot in the gallery, where the former queen resided.

Both complained afterwards of feeling cold and passing out. When they came round they said they felt hot and were sweating.

Visitors have also reported sightings of Catherine, which are supposed to relate to the moment in 1541 when she was arrested for adultery.

She managed to break free from her guards and ran to the chapel to plead with the King to hear her story.

Catherine married King Henry in 1540 at the age of 19 and was executed at the Tower of London in 1542.

The unexplained sightings are to be put to the test next month when the palace invites parapsychologist Dr Richard Wiseman to explain the phenomenon.

A Royal Palace spokesman said: "There have been strange happenings in the Haunted Gallery. There are things that are not easily explained which is why we have invited the parapsychologist to the palace to see how these incidents came about and if they can be explained scientifically."

Dr Wiseman will conduct four all-night vigils in the haunted gallery and will use thermal imaging cameras to detect any changes in temperature, which is one of the most commonly reported phenomenons associated with the paranormal.

He will also be running daily talks explaining the scientific evidence to ghosts and will be canvassing up to 600 visitors to discover what their experiences were.

The event will run from May 27 to June 4. For details ring 020 8781 9500.