In the Doctor Who Children in Need minisode Time Crash, the Fifth and Tenth Doctors briefly meet, and the Tenth saves them from a destructive paradox by cancelling out a supernova with a black hole. He was only able to do this because he had retained his memories of the incident ever since he'd been the Fifth Doctor:

FIVE: Far too brilliant. I've never met anyone else who could fly the TARDIS like that.

TEN: Sorry, mate, you still haven't.

FIVE: You didn't have time to work all that out. Even I couldn't do it!

TEN: I didn't work it out. I didn't have to.

FIVE: You remembered.

TEN: Because you will remember.

FIVE: You remembered being me, watching you doing that... You only knew what to do because I saw you do it.

But we've seen in other multi-Doctor episodes that only the latest incarnation of the Doctor is ever able to remember their shared experiences. From the 50th anniversary special, The Day of the Doctor:

WAR: I won't remember this, will I?

ELEVEN: The time streams are out of sync. You can't retain it, no.

So how come the Fifth Doctor could remember anything at all? And given that he could, how much could he remember? When he finally regenerated into his tenth incarnation, did he think "ah, it's this face - I knew this one was coming"? (Because it sure didn't look like it.) When the Master showed up in Utopia, did he think "ah yes, I remember myself telling me he was going to show up again"?

I realise the answer may just be "timey wimey", but I'm hoping for something a bit better than that.
And this isn't a dupe of this question, which is asking about the bootstrap paradox rather than why the Fifth Doctor could remember anything at all.

  • 1
    Nice question (and I agree, it's not a dupe). My first thought is "timey wimey". But maybe there's a real answer...
    – Praxis
    Commented Feb 20, 2016 at 22:51
  • I wonder if this is a case of the producers retconning cross-time stream interactions and how they work Commented Feb 21, 2016 at 0:44

1 Answer 1


I'll try to explain the best way I can with examples from the 50th anniversary special "The Day of the Doctor". There could be spoilers, so watch out if you haven't watched that episode. I won't give much of the story away...

When The Eleventh Doctor is investigating the paintings in the undergallery, in the first half of the episode, this happens... (emphasis mine)

(The time fissure appears in the under gallery.)

DOCTOR: Oh no, not now.

CLARA: Doctor, what is it?

DOCTOR: No, not now. I'm busy.

KATE: Is it to do with the paintings?

DOCTOR: No, no. This is different. I remember this. Almost remember. Oh, of course. This is where I come in.

(He throws the fez into the fissure.)

DOCTOR: Geronimo!

(And leaps into it himself.)

He says he "almost" remembers. Of course, these events already happened in his timeline, back when he was the Tenth Doctor. In fact, when he meets his past incarnation, they have this exchange:

DOCTOR 10: Okay, you used to be me, you've done all this before. What happens next?

DOCTOR11: I don't remember.

DOCTOR 10: How can you forget this?

DOCTOR11: Hey, hang on. It's not my fault. You're obviously not paying enough attention. Reverse the polarity!

The best explanation I can find is that those events are "locked in" the past incarnation's memories, and when they happen again, out of synch, so to say, something triggers those memories coming back. That's how the Tenth Doctor remembered when he met the Fifth. At first he had no clue, but suddenly, he remembered.

It's been established that when different incarnations of the Doctor meet, only the older one remembers what happened. That explains the Ninth, Tenth and Eleventh Doctor remembering that they destroyed Gallifrey instead of saving it. After Day of The Doctor, the Eleventh remembered, because he did it.

It's all timey-wimey, but I really think this is how it works.

  • The way I interpreted those bits you quote is that all but the most recent will forget events starting from as soon as two (or more) Doctors are together. That would explain why Eleven remembered the fissure and the fez and surmised that "this is where I come in", but didn't remember anything of what happened afterwards.
    – Rand al'Thor
    Commented Feb 21, 2016 at 23:23
  • Exactly. The memories are triggered only when they're necessary, to keep the time loop stable. Doctor 10 only remembered in Time Crash, when he really had to...if it makes sense...
    – tilley31
    Commented Feb 22, 2016 at 16:11
  • But is there any other precedent for a later Doctor remembering what happened when he was an earlier Doctor and they were actually together? In DotD it looks like Eleven remembers what he saw as Ten just before Eleven showing up, but nothing of what happened when they were together - whereas in TC Ten remembers what he (as Five) saw himself doing.
    – Rand al'Thor
    Commented Feb 22, 2016 at 19:49
  • I don't know about precedent. Down here it's tough to find Classic Who episodes, so TC and DotD are the only "multiple Doctors" stories I've seen. It's the best I can do.
    – tilley31
    Commented Feb 23, 2016 at 2:31
  • what do you mean by the events of the 50th are "locked in" the past incarnation's memories, and when they happen again, out of synch, so to say, something triggers those memories coming back. whats the thing that triggers the memories to comeback Commented Apr 13, 2016 at 1:55

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