In the history of Doctor Who, there is one writer who seems to have disappeared into obscurity - despite writing two Tom Baker-era stories, little has been documented about him, nor has there been any critical discussion of his work.His name is David Agnew.
Admittedly, he is a tough individual to track down - he is the BBC equivalent of Alan Smithee, a name that is used when a script editor (or as we Yanks say it, "show runner") cannot/does not take credit for a script he/she has written. Which is, for Mr. Agnew, a shame - for one of "his" scripts is pretty much classic Who...and the other is, well, rather rushed and hastily done...and it shows.
First, the mess - the Season 15 closer The Invasion of Time (actually co-written by script editor Anthony Read and executive producer Graham Williams) wasn't made in the b
est of conditions - an impending strike, an end-of-season deficit of funds, and a failed first attempt meant that both of them had to write a rushed script using existing sets...and it shows. The dialogue is rather spotty, the continuity between scenes is almost non-existent, and the premise (Sontarans invade Gallifrey!) reads like bad fan fiction. Granted, the recent DVD release features some redone CGI effects (which help replace the infamous Chromakey tinfoil aliens, among other things)...but this story doesn't quite come together. There are people who think of this as "Who at its best"....but that would be inaccurate. The rushed nature of these episodes, with the mismatched scenery (interior TARDIS scenes were filmed at an abandoned hospital) and gaping plot holes...well, not even a scantily clad Louise Jameson can rescue this story.(And a sarcastic thank you to Terrance Dicks, who nearly "spoils" the revelation of David Agnew's identity in one of the bonus features with a poorly timed joke).
However, "Agnew's" next script, City of Death 
(with input from the immortal Douglas Adams, as well as Williams and based on a story by David Fisher) is classic. It really is worth all the hype and accolades - Baker's mugging is slightly restrained; the plot is smart and respects the viewer's intelligence, and the overall idea - that an alien being influenced world history and technology to get to a point where it could prevent a disaster - makes it almost epic.
And - it has John Cleese in a very smart cameo.
Episodes penned or directed by pseudonyms are often suspect, much like public domain movies. Why shouldn't someone take credit for a job well-done? (OK, it was BBC policy that if you could not write scripts for a show you were script editing).
In David Agnew's case - at least for one episode - three men: Graham Williams, Douglas Adams, and David Fisher - deserve the lion's share of the credit.
Mr. Agnew, we hardly knew ye.
The Invasion of Time: Not Recommended
City of Death: Very Highly Recommended