User "mengutimur" has put the whole BBC 1964 "The Great War" on YouTube.
Way, way, way better than newer series, which I find too gung-ho "Brits rock, Germans suck, we were right, they were proto-Nazis and the Kaiser was evöl" type of pop documentaries.
I find the old one way more nuanced and balanced. Plus they actually had veterans of WWI, still rather young.
An absolute must see, up with The World at War for WWII.