As many Doctor Who fans know, this was a last minute story with very little budget and so became the first Doctor Who story to be filmed entirely on location.
This is Tom Baker at his best, he injured himself during the making of this and you can tell during part of the fight scene with the Sontaran that a double in a wig was used. Baker is witty and demonstrates the light hearted ego we all love about his Doctor.
A welcome return of the Sontarans. Given the budget restraints Doctor Who often had, the Sontaran costume and make-up is excellent. One of the eeriest characters (and one I hope we'll see again in the new series at some point!). The Sontaran was one of the darkest characters, carrying out experiments on humans as if they were mere labratory specimins. There seemed to be a bit of humour in his beaurocracy obsession with keeping notes too!
The robot was a bit dire - it looked like a couple of coat hangers had been animated through demonic possession, so it didn't scare me. But that's where imagination comes in handy - as with the snake! The accents of the astronauts kept you guessing as to where they were from as you picked up hints of, well, everywhere!
Sarah Jane (Elisabeth Sladen) was a strong character in this episode, perhaps more than Ian Marter who was easing himself into the role still. Interestingly, Tom Baker looked as though he'd been playing The Doctor since the dawn of time, even though he was still pretty new to the role - such was the genius of Baker.
A slow edited story, which adds to the feeling of nothingness and heightens the tension. It's not a 13 part spectacular, it's not the best ever Doctor Who. But it's still good, and a worthwhile addition to any DW DVD collection.