i reckon Lucy just shot him because she had started to see him for the (albeit sexy) git he really was. She was all very doe eyed in SoD but was looking very fed up with him in LotTL. She seemed to know quite alot about him-so i assume she knew about the ring-and i'm guessing it was her who we saw at the end.
but hey! what do i know!!!

well in LotTL she was being beaten and abused by him, you can kinda see why she shot him in the end

Its certainly established in the series canon that Time Lords can have great amount control over the regeneration process. The 2nd Doctor and Romana are good examples. 9 is a good example too as his regeneration actually starts at the console but he stops it dead long enough to try and prepare Rose.

The Doctor's regenerations seem hap hazzard largely because he isn't very good when it comes to Time Lord skills. The Master however is very skilled, so its not beyond the realms of the possible that he simply forced himself not to regenerate. Note in the death scene he does seem to give the impression that he's holding something back, you can sense the regeneration kicking in but he's forcing it back.

I think it's very possible that Lucy shot the Master because he wanted her to; I think he probably had some form of mind control over her.

I don't think the Master will regenerate as Tennant - I think that would be taking the parallels too far and would undermine the dynamic between them.

Well, we all know it's only a program but there are rules that have been established over the years.....

If you accept that what we've seen before is "Canon" , I have no problem with Timelords being able to control their regenerations to some extent. Romana being able to fine tune her appearance is reasonable, especially as DT was able to grow a new hand.
The leap I have difficulty in making is the ability not to regenerate by choice.
The Doctor and other Timelords we have seen regenerating do so without it being a conscious decision. The Doctor has actually "Died" before, and then his body regenerated when his mind was effectively out of the equation, vis-a-vis McCoy to McGann.
I agree with the previous postee who said it was an automatic process and "willing" it not to happen would be the same as willing yourself not to heal a cut or grow hair!
The only time that there is no automatic regeneration is after the 13th body wears out and dies, a-la Edgeworth.

I think it's an automatic process, under normal circumstances, but if the Master was consciously making an effort NOT to regenerate, I think it could be achieved. If someone doesn't actually want to live, if they've given up and lost that will, death can sometimes be inevitable because they're not fighting for life.

I can accept that the Master could choose not to regenerate, but I do believe he's still alive.

I know I'm going backwards here but going back to the original question I think the option was sort of implied at the end of series one. When the Doctor tells Rose he's absorbed the time vortex and "no-one's supposed to do that" she asks if he can do anything about and he replies "I'm doing it now". Maybe it was just me but it seemed he chose to regenerate at that time. Just me?

Interesting thought, but I don't think he was necessarily choosing to regenerate there, more that having absorbed the Vortex, he was dying and the regeneration process kicked in automatically. But you could be right, it's interesting.

Actually, he was shown to have started the process as soon as he was in the console (when he looked at his hand and it was glowing gold), as someone else said, the 9th Doctor here was holding it back long enough to prepare Rose, thus could explain the way he was acting before it, as soon as he felt Rose was ready, he just let go and the Regeneration exploded.

The most likely explanation is that the Master has actually sorted his essence in the ring, and so his physical body can't regenerate. He's actually duped the Doctor into thinking he would opt to die.

However, the problem is that if he used the Chameleon Arch, how come the Master still has his memory? The chameleon arch wipes any memories the Time Lord has, take John Smith and Yana

Perhaps he found some way to modify it?

but being a timelord himself surely the Doctor would know if it was possible to refuse to regenerate?

Good point. He doesn't seem to doubt it so I suppose we shouldn't either. I do think it's possible to refuse to regenerate and if they never brought back the Master and simply left his story there, I wouldn't have a problem believing in it; after all, the Master did get his victory.

I actually came up with the idea that the Master would return looking like DT back before Series 3 began (long before we even knew the Master was coming back).

Back then many people thought that the "vortex energy" the Doctor expelled during the Christmas Invasion contained the Masters essence, put it together with the Doctors hand and you got a new Master.

I had them encountering each other in three different time periods and would have had the Master (or even the Doctor) regenerating at the end of the third encounter.
http://www.digitalspy.co.uk/forums/s...4&postcount=73

There is supposedly a rumour posted on OG that John Simm will be doing some more DW filming in November

Its often been suggested in the series that Time Lords can/do have a means of influencing the process,Romana scene most obviosly, but also the 2nd Doctor's regeneration.

The Master is certainly more skilled when it comes to "Time Lord" things and its quite likely that ability to control his regeneration while concious is one of the ways he is superior to the Doctor. Of course if a Time Lord is unconcious I would imagine survival instincts would kick in and start the process.

There's a rumour over at OG that John Simm is signed up for two weeks filming on "Doctor Who" in November...

EDIT: Ah, Corwin beat me to it...