The second story of series two, Doctor Who--Dalek Invasion of Earth sees William Hartnell's Doctor in a six-part adventure pitted against his greatest nemesis, the Daleks. The Doctor, Susan (Carol Ann Ford), Ian (William Russell) and Barbara (Jacqueline Hill) arrive in the London of 2164, where the Nazi-like Dalek's have turned the remnants of the human race into slave workers or "Robomen", who unfortunately foreshadow Monty Python's hilarious "Gumbies". The Dalek's plan involves a vast mine in Bedfordshire and the final destruction of the human race, while pitted against them is a WWII-style resistance movement led by Dortmun (Alan Judd) and David Campbell (Peter Fraser). One of the most famous of all Doctor Who stories, Dalek Invasion of Earth features such iconic moments as a dalek emerging from the Thames, and a remarkable flight across London showing daleks crossing Westminster Bridge and patrolling Trafalgar Square and the Albert Memorial. Terry Nation's story is almost insanely ambitious for the budget, and while sets and effects are primitive, the location work is highly evocative. Lavishly remade for the cinema as Daleks Invasion Earth: 2150AD (1966), the plot here is more detailed, mercifully free of comic relief, and delivers a surprisingly sensitive ending to mark Carol Ann Ford's departure from the series.

On The DVD: Doctor Who--Dalek Invasion of Earth is a comprehensive two-disc set with a generally excellent black-and-white 4:3 picture and mono sound. The highlight of Disc One is a warm and very informative commentary hosted by Gary Russell and featuring director Richard Martin (all episodes), producer Verity Lambert (5 episodes), Carol Ann Ford and William Russell (4 episodes each). There are optional subtitles for the episodes, as well as for the commentary, and further text titles giving detailed background information. Optional new CGI-effects shots have been added, which via seamless branching can be selected over the original 1964 model work. The new material obviously lacks authenticity, but looks about 1000 times better. Disc Two offers an abundance of extras including an amusing extract from Blue Peter (6 min) showing how to make edible Daleks. There is a photo gallery and some very poor quality Rehearsal Footage, but most fun of all is a 27 minute 1994 BBC spoof radio documentary which asks Whatever Happened to Susan Foreman?. Jane Asher plays Susan in an SF comedy as ingenious as it amusing and irreverent. This is a remarkable set, which belongs in any Who fan's collection. Gary S Dalkin

Doctor Who: Earthshock finds Peter Davison's Fifth Doctor nicely settling into the role, initially displaying some crotchety short temper that harks back to William Hartnell's incarnation of the Doctor, effectively setting up the most emotionally powerful finale in the show's 26-year run.

In this, the penultimate adventure of Doctor Who's 19th season, a scientific expedition in a cave system on 25th-century Earth is wiped out. An army rescue unit led by Lieutenant Scott (James Warwick) and including the one woman, Professor Kyle (Claire Clifford) who survived the original massacre, goes in to recover the bodies. The scenario deliberately evokes Ridley Scott's Alien (1979), and uncannily foreshadows James Cameron's Aliens (1986), developing into a tense actioner on a space freighter bound for Earth carrying a very deadly cargo of Cybermen.

Tightly paced, refreshingly free of the camp humour that sometimes blighted the show in the 1980s, and with a notable guest turn from Beryl Reid as the ship's captain, Earthshock is one of the Doctor's finest adventures. Overlook a few gaping plot holes and by the end they simply won't matter; when the final credits roll in silence the effect is as powerful now as it was shocking to audiences back in 1981. If only Star Trek: The Next Generation had done the same to Wesley Crusher!

On the DVD: Doctor Who: Earthshock is presented in the original broadcast 4:3 with a near flawless picture, though the source videotape does show just the occasional sign of damage. The mono sound is excellent. The extras begin with a strong 32-minute documentary, more retrospective than making-of. Then comes the commentary, with Peter Davison, Janet Fielding (Tegan), Sarah Sutton (Nyssa) and Matthew Waterhouse (Adric), which like so many Who commentaries is both informative and wonderful fun. Both commentary and the episodes have optional subtitles. Other options include detailed on-screen information titles, an isolated musical score, and the ability to watch with selected effects shots replaced with new computer graphics. There's a scored, five-minute photo gallery that even includes a shot from the recording of the commentary, a pointless assemblage of the seven minutes of footage shot on film, and a three-minute clip montage set to a dreadful techno reworking of the title theme to celebrate the show's 40th anniversary. Much more interesting is a 10-minute section from arts review Did You See? looking back on the show's aliens, and including clips from Earthshock, while the very brief Episode 5 is a hilarious new animation. --Gary S Dalkin