I am not clued in enough to say, with certainty, this BBC drama was impartial - but given how i suppose it could have gone, i think it was close enough. Even if you don't agree, you cannot fault the acting and the direction of this mini series.
Loosely told from the perspective of two foreign office clerks - one German, one British - depicts the many sad, unfortunate and ironic events in the 37 days leading to the deaths of ten million men and women around the globe during WW1.
I am of a generation of kids whose history lessons saw WW1 being completely overshadowed in favour of WW2 - so for me this was particularly interesting. It could have been poorly acted, badly directed and cheap to make and I would still have found it interesting. That it was none of those things was a great bonus! It was obvious from the outset that while they were speaking in English, the German actors were German, the Russian actors Russian and so on. Which added some authenticity to the whole thing (I am a stickler for accents!).
If you want 3 hours of world history and a good account of the bumbling old gits that ran Germany and Great Britain at the time - give this a go :)