Features the return of the glorious Sontarans who miraculously were not bollocksed-up by appearing in NuWho and actually came off pretty well in these episodes.
Martha and UNIT summon Ten (David Teflon) and Donna (Catherine Tits) for help with ATMOS (Atmospheric Omission System), a revolutionary piece of green technology installed in 400 million cars worldwide which is later revealed to be part of a Sontaran plot to poison Earth and kill everyone.
Those wacky manlets, when will they ever learn?
Featuring the rather awesome General Staal the Undefeated, played by Christopher Ryan (Mike from The Young Ones).
No one actually remembers this episode. It may as well be not canon.