I got Enemy Of The World too. Is remarkable how the writing leaps in quality from rather stodgy stories like The Savages (nice ideas but written like a couple of five year olds recounting the plot) to similarly idea rich tales like that just a few years later.
Troughton's accent is terrible but his body language is a masterclass of acting.
Two totally different characters and the nuances employed when they each have a go at impersonating each other.