'THE FIVE DOCTORS' AT 40: MYSTERY AND DANGER WITHIN THE DARK TOWER OF RASSILON!

With the Fifth Doctor unexpectedly making a trip to Gallifrey (via a commandeered transmat device previously given to the Master) and now investigating the culprit behind the activation of the Dark Tower, Doctor One and Tegan travel to the Dark Tower so as to deactivate the building's force field facility, in order that Susan and Tegan can pilot the TARDIS to their ultimate location. Soon enough the pair encounter the Master and a troop of Cybermen, whom the supervillain soon murderously double crosses in order to gain full access to the Tower and its potential powers. 

Doctor One and Tegan use an entry coder to gain access to the main door entrance to the tower.

Sarah holds on to her metal rope for dear life as she and Doctor Three swing their way over to the roof of the tower.

A lovely posed publicity image of Jon Pertwee and Elisabeth Sladen at Ealing film studios.

The Master and the Cybermen, now in league, enter the Dark Tower's main reception area.

The Master deliberately leads the Cybermen across a chess board like floor knowing that it is ladled with deadly energy weapon traps.

The Cybermen are soon destroyed.

And the Cyberleader (David Banks) quickly blasted into oblivion by the Master, in one of actor Anthony Ainley's favourite moments for his character from the series.

The Master gives Tegan and Doctor One some subtle information about how to traverse the deadly checker board floor. It's as easy as Pi!

Doctor One works out the risky mathematical formulae to cross the death board.

Going deeper into the heart of the tower, strange fears and forebodings affect Tegan.

The Third Doctor encounters the phantom forms of Mike Yates (Richard Franklin) and Liz Shaw (Caroline John).

Posed publicity image of Caroline John.

Posed publicity image of Mike Yates (Richard Franklin).

Meanwhile, Doctor Two and the Brigadier, having encountered a Cyberman in the zone and survived a brush with a Yeti creature left over from the Dark Times, make their way into the tower from below and encounter mysterious phantoms of their former friends Jamie and Zoe. At the same time, Doctor Three and Sarah Jane Smith, having reached the Tower via mountain cable swing, enter the interior as the Doctor encounters his own phantoms in old friends Captain Mike Yates and Liz Shaw.

Doctor Two and the Brigadier enter the Dark Tower from its underground passage.

They encounter the phantoms of Jamie (Frazer Hines) and Zoe (Wendy Padbury).

The Doctor breaks the phantom spell with a matter of memory that will fascinate and frustrate series fans in equal measure.

Frazer Hines and Wendy Padbury in a moment together between filming.