The Two Doctors is an unusual Multi-Doctor story. It wasn't to celebrate an anniversary (NB: This is less unusual nowadays, with Twice Upon A Time having happened outside of an anniversary too), it doesn't feature a major catastrophe that brings the Doctors together and weirdly of all, it doesn't feature much Multi-Doctor action.

The latter is also its flaw. The lack of screen time with Colin Baker and Patrick Troughton onscreen together ultimately means Patrick Troughton's talents feel wasted. You've got two great actors: why not show them together more? They only interact together near the end of the story and the serial is comprised of three 45 minute episodes. 135 minutes and there's hardly any Patrick Troughton/Colin Baker interaction!

The Sontarans are ridiculously tall also. Somebody on the production team clearly missed the memo that they are supposed to be small. Sometimes this can be distracting to the story as you're wondering why, when the Sontarans are a clone race, two of them would be taller than others seen in the series.

The plot is interesting though. It sees the Sontarans try to take the symbiotic (that allows safe travel through time) from the 2nd Doctor, messing with his DNA and turning him into an Androgum. Meanwhile, Androgum Shockeye has a strange fetish for people and chases Peri (Nicola Bryant) around intending to cook her. Shockeye (John Stratton) is a great villain and one whom I wouldn't mind seeing return in the new series; he seems genuinely disturbing, especially the way he leers over Peri in one of the cliffhangers.

I also like the idea of the Time Lords sending the Seconc Doctor and Jamie on missions. This seems to tie in with the popular fan theory 'Season 6b'; the idea was that there was an off-screen season between Patrick Troughton's last and Jon Pertwee's first where the Second Doctor was sent on secret missions by the Time Lords before his regeneration and was reunited with Jamie. The biggest clue that The Two Doctors makes this canonical is that Patrick Troughton looks visibly older. It can't be time differential as it is noticeable when he and Jamie are in the TARDIS together - no 6th Doctor present there - and unless the Time Lords wipe the Doctor and Jamie's memories it cannot take place before The War Games as the Doctor didn't tell Jamie about the Time Lords before then.

If this seems heavy on continuity, you can blame my review not the serial. The Two Doctors is a good story but it is let down by a disappointing lack of Multi-Doctor action and a silly decision to make the Sontarans tall.