Ace came bounding into the TARDIS control room, full of her usual energy, still drying her hair on a towel. "Morning, Professor!" she said cheerfully.

The Doctor, looking as usual like a friendly, overgrown leprechaun, beamed at her. "Good morning, Ace. And I'm about to answer your question."

Ace raised her eyebrows. "What question?"

The Doctor depressed a lever on the control panel and the grinding engine noise began. His expression suddenly became serious. "You remember that nasty business with Lady Peinforte and the Cybermen, just a little while ago?"

"I'm not likely to forget it!" said Ace.

"Then you'll remember how Lady Peinforte threatened (with the Doctor's Scottish accent it came out as "thrrrreatened") to reveal my true identity to everyone?"

"Yeah," said Ace.

"You could see that I was really alarmed by Lady P's threat?"

"Yeah! I've never seen you looking so freaked out."

The Doctor raised an eyebrow at the expression "freaked out", but forbore from commenting. "And you asked me yourself, a little later on, who I am?"

Ace just nodded this time.

"Well," said the Doctor, "I think it's time for me to answer that question. And here is the place to answer it." With that he hit the control to open the TARDIS doors, and swept out. Ace hurried out after him.

When she saw what was outside, Ace's first thought was of photos she had seen of the immense ruined temple complex at Angkor Wat in Asia. The TARDIS had popped down next to an enormous ruin in the middle of an alien jungle.

The atmosphere was hot and stuffy but breathable. The sky was a sort of purple, different to the skies of Earth, and the plants and flowers were slightly wrong in colour. Most amazing of all, however, was the enormous ruined structure that towered over their heads. It was badly damaged and parts of the wall had fallen in; vine-like plants were starting to grow over the shattered walls as the jungle started to reclaim it. But even so, the immense pile of masonry towered up and up into the sky until it culminated in a huge dome like that of St Peter's in Rome.

The Doctor gestured at it with the umbrella that seemed to be permanently affixed to his body whenever he left the TARDIS. "Impressive, yes?"

"Sure is," said Ace. "What was this place?"

"A palace," replied the Doctor. "The palace of a great and cruel dictator, who ruled this and a number of other planets…." He gave a heavy sigh and looked straight at his companion. "Me!"

Ace laughed. "You?" she scoffed. But then she saw the Doctor's expression and stopped laughing.

The Doctor sat down on a nearby rock and signaled to Ace to sit down next to him. As she settled into position he began talking softly, almost dreamily.

"I have never told anyone….. Well, Susan knew, because she was with me from the start, and Romana knew, because it was all in the files…..But I've never told anyone how I left my home planet, or why…..It's time I told someone. The thing is, I used to be quite powerful in politics, back home on Gallifrey."

Ace laughed out loud again. "You, a politician?"

"Oh yes. This was all a very long time ago – hundreds of Earth years ago – but I, along with two other fellows, ended up running the place. A triumvirate, if you like. There were three of us: Rassilon, Omega and myself. We made a great team. Omega was the technical genius – he found a way to get energy from black holes, and he really set the standard for time travel technology – TARDISes as we have them now are pretty much his invention. Rassilon was the statesman, the lawgiver – he organized Time Lord society, set up the government, and established the Laws of Time. I was a sort of trouble-shooter – Prime Minister to Rassilon's President, if you like – and for a while the system jogged along really nicely."

The Doctor seemed to lose himself in his memories for a moment. Ace brushed off an ant-like creature that was trying to crawl up her leg and said, "What happened?"

The Doctor frowned and said suddenly, "You know, I'm worried about the Daleks. A lot of them did survive that business with the Hand of Omega – there's no way we could have killed them all, unfortunately. I've heard rumours that the surviving Daleks are regrouping and planning an all-out war on Gallifrey – the home of the Time Lords. A Time War, they're calling it. That would be madness! But if the Daleks do go all out, using their own time travel technology .. That could lead to all sorts of disasters…"

Another sigh, then the Doctor seemed to come back to the present moment. "Sorry, Ace. Where was I?"

"You and Rassilon and the other geezer."

"Oh, yes. Well – the triangle is a notoriously unstable structure in politics, and basically, after a while, the other two decided they could manage without me. I think it was really Omega – the 'other geezer'. He always did have a big ego to go with his scientific brilliance. Somehow I think he persuaded Rassilon that they didn't need me. In human terms, there was a 'party room coup' and they dumped me."

"That's awful!" said Ace.

"Oh, I don't blame Rassilon. He was the greatest Time Lord of us all – our Winston Churchill, our George Washington, our Abraham Lincoln. It was others – particularly Omega – who turned him against me. But then…. Well, that was when the trouble really started."

Ace adjusted her backside on the uncomfortable rock and asked, "Why? What happened then?"

The Doctor looked at Ace with haunted eyes. "Because I, to put it mildly, took it very badly indeed! This sense of betrayal by my own friends, being stabbed in the back by the people for whom I had worked so hard….. I suppose in recent Earth jargon you'd say I turned to the dark side! I became obsessed with hate and revenge, with getting my position back. I stole a TARDIS – the same old one I still use. I left Gallifrey, the home world, and came here – to this planet, Tarcisius Minor. I set up my base here and started raising an army."

The Doctor wiped his brow as it was getting quite hot and muggy. Ace was looking at him in disbelief. "You – raising an army?"

"I was such a different person then – evil, full of malice and ambition. And I had three accomplices from my own race: people I had known and worked with before, they helped me set myself up here. We built our own space navy, recruiting the natives of this planet and neighbouring planets - trying to set ourselves up to attack Gallifrey, the way the Daleks are now." The Doctor stood up and looked round. "This was my capital city… My palace right here, an enormous monument to my own ego; a grand avenue down there, the 'Avenue of Victories'; and a public square just over there, were we had public executions of people who defied my authority." He looked at Ace, the haunted expression in his eyes again. "I have to live with that…"

Ace reached out and touched his arm, silently. Then the Doctor went on, "It all came to an end very suddenly. I thought I had hidden my exact location from them, but the Time Lords sent a TARDIS team directly into my palace – right into my living quarters! – to deal with me, much the same way the Americans did with Bin…"

"With who?" Ace asked.

"Sorry, he's in your future, I can't tell you about him. Anyway, I refused to surrender, and I was shot – and badly injured. While I was recovering, Omega had his accident with a black hole. We all thought he'd died, though it later turned out he was trapped in another universe on the other side of the black hole. Anyway, with him out of the way, Rassilon realized he had treated me badly and came to me in hospital and actually apologized to me – he asked for my forgiveness, after all the terrible things I had done! He really was the best of us all. After that I changed. I suppose I had a sort of mental breakdown, and realized what a monster I had become. I spent days in my cell just screaming with guilt and horror. I was ready for them to execute me, or put me in jail for an eternity. But then Rassilon came to me again and offered me a deal."

"Oh, Professor," Ace said. "Just one thing. You said you had three mates – three henchmen – who were also Time Lords."

"Ah, yes. They managed to escape while the Time Lord authorities were concerned with catching the ringleader – me! They're still out there, I'm afraid – still causing mischief. I've had run-ins with all three of them since then: the Master, the Rani and the War Chief…."

There were a few moments of silence while the Doctor gazed into the past. Then Ace prompted, "You said whatisname, Rassilon offered you a deal?"

"Yes. It was either a public trial and execution or… "

"Or what?"

"Exile. Officially, a life of exile. Unofficially, being a sort of roving free agent. You see, the Time Lords have always had this strict policy of non-interference in the affairs of other planets: only observe, never interfere. The river of time must always flow unimpeded; we can never interfere in the course of history. Rassilon himself was very strong on that – at least in his official pronouncements. Just quietly, however, he realized that he might need someone out there to act – strictly unofficially – for the Time Lords when things did arise that needed some discreet attention. On paper I was an exile with no official standing, so the Time Lords could always deny they had sent me."

"Plausible deniability," Ace scoffed.

"Exactly. Politicians are the same on every planet, I suppose! Anyway, even though I was still feeling so guilty I wanted to die, I accepted Rassilon's offer. He gave me back the same clapped-out TARDIS I had stolen earlier, gave me a young Time Lady to act as my minder, and off I went."

"A Time Lady?"

"Yes; she became more like my nurse after a while. She even used to call me 'grandfather' – it started as a joke. You see, I was quite old by then, and the strain of my rapid rise and fall from power had aged me even further. I was near the end of my first lifetime – my first incarnation. We lived on earth for a while – a planet I already knew and liked – while I fixed up the TARDIS and recovered from my mental breakdown, I was probably quite grumpy and irritable in those days; I must have been hell to live with! "

"Oh, so the Time Lady – that was the Susan you've talked about earlier?"

"Yes – the first of my many travelling companions! That was London, 1963….. I'll never forget it."

"Coal Hill School! We went back there!" Ace remembered.

"We did indeed. And now … that's enough of this walk down memory lane. I do feel better for having talked about this and getting it off my chest. Thank you for listening, Ace."

"A pleasure, Professor. Don't they say confession is good for the soul?"

"They do indeed." The Doctor offered Ace his arm. They got up off the rock and went back into the TARDIS. The door closed, the grinding dematerialization noise started up, and the blue box that was the TARDIS's external shell faded away…..

And a few seconds later, a young, frizzy-haired female archeologist popped up from behind a nearby fallen statue, where she had been hiding and listening to every word that was said.

"And just who was that?" wondered River Song.