"Spearhead from Space" was the only classic Doctor Who serial to be shot entirely on film (as opposed to videotape) and therefore it's the only serial that can be easily converted into high definition and presented on Blu Ray. Hence this release -- the only 1970s Who story in the Blu Ray pipeline, for the time being.
Now, long-time fans will no doubt be aware that Spearhead has been released before, on VHS and DVD (twice). Thus, we all face a burning question...is it worth triple- (or quadruple-) dipping and buying this same story yet again, in a new format?
The short answer is, yes. The Blu Ray edition of Spearhead has a much nicer print than even the recent DVD special edition, with vivid colors and details; indeed, it simply blows away the washed-out prints of this story that I remember from back when I was a kid. To cite just two examples of how good this print is, I was able to admire the stitching on Jon Pertwee's shirt, and I noticed for the first time that the main villain has yellowed teeth.
That said, Blu Ray is a bit of a double-edged sword. The clarity of the print allows you to see extra detail, but also (in my opinion) makes film grain much more obvious and distracting than it looks on DVD prints. For this release, the Who Restoration Team cleaned up some of the grain but stopped short of "polishing it out" completely, which I think was a good move. The resulting presentation is not totally pristine but still very nice, and looks comparable to other Blu Ray prints of movies/TV shows from this period.
Now, on to the prickly subject of special features. The main offerings on this Blu Ray are two excellent (if a little sad) documentaries on the late Caroline John and Jon Pertwee. They're both presented in high def, and feature touching tributes to the actors from their colleagues and friends/family. But here's the problem. Older DVD releases of Spearhead featured different special features, including an excellent "making-of" documentary about the serial itself. And those features haven't been carried over to Blu Ray -- much to my chagrin. I find it quite annoying that I now have to keep my old Spearhead DVD, in addition to this Blu Ray, because the features are different.
And I can think of no decent excuse for why the DVD features couldn't be carried over to this Blu Ray. Perhaps the old features were shot in standard definition instead of high def...but so what? When Paramount re-released the Star Trek movies on Blu Ray, they carried over the standard definition features from the DVDs and also presented a few new high-def ones. I much prefer that approach. So if the BBC plans to release more old Who on Blu Ray, I think they need to get their act together and start carrying over the DVD features. Otherwise, we'll all be stuck with two huge and expensive Doctor Who collections, each with their own set of documentaries. Yikes!