The Very Earliest Dr Who Theme Remix
 

How early? Well, before you were born. :P

Pink Floyd - One Of These Days (Studio version) (6.88MB .wma file).

It's easy to hear but brief enough to miss. Below is a link to a live recording of that song. It's a whole lot more obvious in the live version, although it's quieter.

Pink Floyd - One of These Days (Live) (896KB (yes, it is that small - crap quality) .wma file).

Nice to know that the minds behind and in Pink Floyd were Who fans (in both senses of the word (The Who and Dr Who!). This is a great song anyway - great bass and slide guitar - but the Dr Who bit is an added bonus, is it not. :)

I just noticed that myself a while back. Very cool! :D

it runs for quite a while in the bass line.

Wasn't the very earliest remix made in 1963? The original full-length version cut together to make the "Titles" version of the theme... ;) </pedant>