M is for... Master (5)

Following the events of the Last Great Time War, the Doctor believed that he was the sole surviving member of his people. However, the dying Face of Boe had once told him "You are not alone".

During an encounter with the ruthless Family of Blood, his companion Martha Jones had seen the Doctor conceal both his personality and biological identity using a Chameleon Arch. This Time Lord technology was present in every TARDIS, and it rewrote the biology to make its user appear to be human. A whole new personality, complete with artificial memories, was generated.

The Time Lord's true identity was stored within an ornate fob watch, protected by a low level perception filter. Once opened, the fob watch restored the user to their normal state.

After stopping off briefly at Cardiff Bay to refuel from its space-time rift, the TARDIS had been thrown forward to the very end of the universe by the arrival of Captain Jack Harkness. The ship took them all to the planet of Malcassairo in a failed attempt to shake him off.

Here, they encountered one of the last groups of human refugees, who were planning to travel to a place known only as "Utopia", where humanity was gathering. An elderly scientist named Professor Yana was responsible for completing the rocket which would transport everyone, assisted by one of the last surviving natives - the insectoid Chantho.

The old man was troubled by a constant drumming in his head. He claimed to have lost his memory - having been found as a "naked child" in a region known as the Silver Devastation. His only possession? An old fob watch... 

Martha saw this and recalled her earlier experience with the Doctor. Talk of TARDISes and time travel had already stirred some distant memory in him, and now she had drawn his attention to the watch - overcoming the perception filter. Opening it, he released his original identity - that of the Master.

He had been resurrected by the Time Lords to fight in the Time War but had run away after witnessing the Dalek Emperor's seizure of the Gallifreyan Cruciform. He had used a Chameleon Arch to conceal his true self, and thus become the human Professor Yana.

The Face of Boe had cryptically referred to him in his prophesy - You Are Not Alone. 

Once he had regained his memories and personality he turned against Chantho, electrocuting her. He then set about sabotaging the rocket compound from which the refugees had now departed for Utopia, allowing the cannibalistic Futurekind to enter. He was planning to steal the Doctor's TARDIS, but was shot by the dying Chantho. Locking himself in the TARDIS, he realised he was going to regenerate. If the Doctor could have a younger body, then so could he...

Played by: Derek Jacobi. Appearances: Utopia (2007).

• Following an already successful stage career, Jacobi gained wider public acclaim by playing the titular Roman Emperor in I, Claudius (BBC 1976).
• He claimed that his TV career ambitions were to appear in Coronation Street and Doctor Who.
• He had already portrayed a version of the Master in the animated serial "Scream of the Shalka". This had been an android version, created by the TARDIS following the events of the 1996 TV movie.
• When Jacobi's I, Claudius co-star John Hurt passed away, Big Finish avariciously switched from "War Doctor" stories to "War Master" ones. These take it that he was already in his older body before using the Chameleon Arch. However, if you don't follow the audios, then his entire life as a human was post-Chameleon Arch and he really was found as a child. The BF scenario does not stand up to close scrutiny - why would the "War Master" run away from the conflict after fighting in it so long? It is much more likely that the self-serving Master ran away early on. Russell T Davies himself suggested this.
• Utopia saw the first ever on-screen regeneration that wasn't the Doctor's.