Complex sentence: Nicholas Courtney reappears as Brigadier Lethbridge-Stewart in "The Invasion", last seen (as a Colonel) in "The Web of Fear", and would soon make regular appearances in the program beginning with season 7's "Spearhead from Space".
Split into simpler sentences: Nicholas Courtney reappears as Brigadier Lethbridge-Stewart in "The Invasion", last seen (as a Colonel) in "The Web of Fear". He would soon make regular appearances in the program beginning with season 7's "Spearhead from Space".