This list has also stayed clear of any classic episode with more than four parts - and for good reaso, too. They generally can become long drawn out affairs and even the greatest stories have moments where they hit a slump or start to repeat themselves. At the same time, the great multiple-episode stories - the really great ones - have such an epic scope to them that has rarely been replicated in Nu Who. The Seeds of Doom is one such story. As well as one the greatest Doctor/companion relationships in the show's history in the Fourth and Sarah Jane, it also features two great villains in Harrison Chase and the alien menace that is the Krynoid. It evens gives viewers one of their last rates of UNIT, even though it doesn't feature the main players like the Brigadier. It has a sense of grandeur too - the first two episodes set in Antarctica are a virtual claustrophobic recreation of The Thing before it heads back to England for the final four episodes in the ultimate homage to Day of the Triffids. A cracking cast, an epic monster, multiple brilliant cliffhangers and Tom Baker and Elizabeth Sladen at their best. If you're not sold on Doctor after this story then this show probably isn't for you. Of course, if you find yourself loving multiple-episode stories, then you might be ready for Inferno, The Talons Of Weng-Chiang and the greatest Doctor Who story of them all: Genesis of the Daleks.