"The Romans" is an absolute delight. The reason I never seemed able to enjoy the early historicals as much as many other "Doctor Who" fans is that as a minor history buff I knew exactly what was going to happen and what purpose the characters would serve. The only great historical story prior to "The Romans" is "Marco Polo" which overcomes the predictability and lack of intriguing plot by the sheer quality of its script and characterization.
With "The Romans" Dennis Spooner takes a more novel approach to the "Doctor Who" historical and makes the story the first true "Doctor Who" comedy. Of course, much of the comedy would now be considered dark, cruel, and even hopelessly politically incorrect (the most comedic episode of the story is based around attempted poisoning and attempted rape or at least sexual harassment). I don't think the story is THAT dark, certainly much of the comedy would have seemed black even in 1965, but it's all done with such a panto vibe that it's hard to take it seriously on any level, at least the more obvious flat-out jokes- there's a few ones that'll slip by you if you aren't paying attention that were clearly aware of how serious the situations actually were. The script is just generally superb, with all the characters, gags, and dialogue working wonderfully well in the story. "The Romans" works especially well for me now that it's not a bootleg audio cassette my father bought when I was five because I can pick up on the pastiche and satire elements in "The Romans". In many ways it is the first historical to really do something daring and interesting with the material as opposed to simply excel at something good but obvious ("Marco Polo").
'Directed by Christopher Barry' is basically a statement regarding the quality of direction in the story. "The Romans" is excellently directed, and if you give Barry any credit at all for Derek Francis' utterly hilarious take on Nero we can call his work 'superlative'. Derek Francis may steal the show, but Maureen O'Brien makes quite an impact in her first real adventure with the Doctor. I always found it a bit aggravating when people dismiss Vicki as Susan 2.0 as despite the similarities I found the dynamic between Vicki and the Doctor very different than the dynamic between Susan and the Doctor. Vicki is also just more fun to watch as she exudes glee and thrill at her suddenly adventurous lifestyle. The rest of the regulars also get a chance to shine, with William Russell, Jacqueline Hill, and Hartnell all clearly having fun with the material, especially Hartnell who can't have imagined he'd be getting to do a fight scene at his age.
"The Romans" is perhaps my favorite "Doctor Who" historical. It is really just an absolutely wonderful story that never stops being thoroughly entertaining.
Episode 1: 8/10, Episode 2: 9/10, Episode 3: 10/10, Episode 4: 9/10.
Average: 9/10