Ah, that would have been "The Sontaran Experiment" with Kevin Lindsay in his second (and tragically last) appearance as a Sontaran. Lindsay played the first Sontaran , Lynx, in the Jon Pertwee adventure, "The Time Warrior", which also introduced viewers to Elizabeth Sladen as Sarah Jane Smith.

Anyway, TSE followed the events of "Ark In Space" when the Doctor, Sarah and Harry Sullivan teleport down to Earth from Space Station Nerva. The Doctor had decided to check out conditios for the newly revived crew of the station, making sure it would be okay for them to inhabit the planet again (after it had been ravaged by solar flares). But unknown to the Doctor, the Sontarans had finally taken an interest in Earth as a strategic location in their war against the Rutans. Field Marshall Styre had not expected to find any sentient beings on the planet, but since he did, he wanted to investigate their potential, physically, mentally and militarily.

Lindsay's costume was considerably modified for his second appearance. While the "spacesuit" was essentially the same, the headpiece was new and considerably reshaped and differently colored. Not a problem except for the fact Sarah was initially confused, thinking Styre was actually Lynx, even exclaiming they looked exactly the same. Hardly, Lynx's head was a bit more narrow, almost chocolate colored and had hairy bristles over his eyes and under his lower lip. Styre had a wider head, ashen skin and was devoid of any hair. Styre was also the only one to have 4 fingers and a thumb per hand while every other instance, both classic series and current have depicted them with 2 fingers and a thumb.

Uh, sorry about that. Got a bit long winded. Anyway, thanks for the kind words about my efforts.

Sincerely,

Bill

Tempt the Hand of Fate and it'll give you the "finger"!