The entire film is a gem, but I loved seeing the full clip of 'Germany Calling' , the Lambeth Walk in the special features section.
here is a rather grainy clip of it from YouTube; the supplemental features clip is outstanding
http://www.youtube.com/watch?v=F6vCIEG0Bxc
this is another great one on the Lambeth:
http://www.youtube.com/watch?v=jGNfNYpfH74