[5] However, in March 2009, Staffordshire Moorlands District Council accepted planning permission for the ride (with conditions) and groundwork construction commenced about three months later.

The initial idea for the secret element originated from a previous rollercoaster plan that he designed for Alton Towers, in which a piece of track tilted back and forth during the ride.

The Alton Towers marketing team made an effort to keep the "world's first" element secret so that the surprise feature would not be revealed until the ride was opened.

In 2008, concept art showing possible themes for the new ride were leaked online but only appeared briefly after they were deleted at Alton Towers' command.

Alton Towers released a new marketing campaign later inviting readers to "Ride the Demon of the Dark Forest" and "Surrender in March 2010".

These included a video of a truck supposedly delivering the "secret weapon", and three promotional blipverts which featured a possessed girl walking in a forest.

The advert also uses a short but 'darker' rendition of the Alton Towers theme music (Edvard Grieg's In the Hall of the Mountain King), driven mainly by the harp and piano.

An early press release initially stated that thirteen - deemed to be the scariest rollercoaster ever created (with a world's first element) would require a signed waiver of liability just to ride.

Sections of the outdoor track have been fitted with speed-reducing devices due to early problems with the ride entering its second lift hill too quickly.

[18] This surprise sequence consists of a horizontal section of track, on which the train stops, which freefalls downwards, making Thirteen the world's first vertical free-fall roller coaster.