Fight against Skagra
The Fourth Doctor and Romana II were engaged in a fight against Skagra in Cambridge. (PROSE: The Universal Databank [+]Loading...["The Universal Databank (reference book)"], TV: Shada [+]Loading...["Shada (TV story)"])
Some time following the Fourth Doctor's regeneration, the series of events involving the Doctor and Romana's defeat of Skagra (TV: Shada [+]Loading...["Shada (TV story)"]) were prematurely aborted when the two Time Lords were caught in a Time Scoop sent from the future by Lord President Borusa during his gambit for immortality. Though it was intended that the Fourth Doctor would join his previous incarnations and their companions in the Death Zone, the attempt to lift him from his time stream was unsuccesful and his was trapped in a time vortex which endangered the existence of the Fifth Doctor. After Borusa's plot was foiled, the Fifth Doctor was assured by Rassilon that his previous incarnation would be freed, with the Fourth Doctor and Romana seemingly being returned to resume the natural course of events. (TV: The Five Doctors, WC: Shada, et al.)
However, in the post-Time War universe, the author of A Brief History of Time Lords acknowledged a theory that temporal instabilities had caused the chain of events to unfold on at least four occasions, involving at least two different incarnations of the Doctor. (PROSE: A Brief History of Time Lords) Indeed, one account of the event presented the Eighth Doctor and Romana, who by that point had been elected President of the High Council, at one point "resuming" their adventure. (WC: Shada [+]Loading...["Shada (webcast)"])
Behind the scenes
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A future incarnation of the Doctor, who appeared as an older version of the Fourth Doctor, found himself in a museum displaying exhibits of several of his past adversaries. After encountering the Krarg exhibit, the Doctor recalled his "cancelled" adventure involving Skagra and — with only partial records remaining — proceeded to recount the missing scenes. (HOMEVID: Shada)
