This is one of those trivial but niggling questions that DW throws up now and then: what happened to the StJohn's Ambulance Badge on the TARDIS door and how many times has it returned over the years? In celebrating the 47th Anniversary on Tuesday, HWMBO and I watched the Pilot of "An Unearthly Child" and the edited Pilot and then the Broadcast episode...Badge present in the first two, gone by broadcast...anybody care to speculate (or actually know) why this was?

The badge's last appearance, IIRC is in "The War Machines", William Hartnell 1966.

The doors were given a fresh lick of paint, but they painted over the badge and didn't replace it. Its first full reappearance is in the Matt Smith series. (any other reapppearances occur on model shots, where the badge can be seen on the model tardis )

The repainting was actually done during filming of that story so the badge is seen in some shots (ones done in the studio I think) but not others.

That's what I meant

The model shots in that story have the badge too, but the accompanying location shots were done after the badge was painted over

I have a theory that the Tardis always retained the general police box shape, but the chameleon circuit had occasional shivers, meaning little details changed. The St. John's Ambulance badge went. In some stories, the Tardis has a "stacked" roof, in some stories it doesn't. A couple of times, it appears without the light on top.

In the last few years, the Tardis has remained constant, until the explosion at the end of End of Time caused the chameleon circuit to have another big shiver. From early in The Eleventh Hour, it's constant again.

Oh, I like that theory, sort of smooths over the continuity errors and makes everything ok in your head!

Thanks, DoctorQui! It neatly allows everything to be explained away. I'm sure it could be extended to explain away other niggly stuff like the Tardis landing silently in a couple of stories, or the Tardis taking off like a rocket in a couple of stories.

As the first Doctor said, "this doesn't roll along on wheels, you know"!

It only rockets off when the Doctor wants to show off

You're in good company as Mark Gatiss suggested that in a New Adventure called St Antony's Fire back in around 1994/5.

He called it chameolonic flicker or similar and in that story the St Johns badge reappears.

The badge is on the TARDIS in the location filming for War Machines and had gone by the studio session for episode one. At the same time the white edge windows are painted blue. Those also only reappear with Matt Smith.