Could this have been the BBC's dummy run for I Claudius? Made in 1974, two years before I Claudius, there are so many similarities - from episodes written by Jack Pulman to the style of having most of the drama arising from actors in a studio set talking to each other. Plus there is a considerable cast overlap.
The period sets and costumes in Fall of Eagles are every bit as impressive as in I Claudius, though the directing lacks the superbly-timed dramatic flourishes that help consolidate the later series in its rightful position at the pinnacle of BBC drama. Unlike I Claudius, this series does have a significant amount of location filming, but then that would be easier for a series set around 100 years before it was made than 1900 years (or near).
The subject matter is the fall of the three Emperors of Germany, Russia and Austria in the period of 1848 to 1918. So additional similarities to I Claudius can be seen to be the setting over a span of years with the main characters aging as the episodes pass, and the minor characters all coming and going as required. The theme is also similar, dealing as it does with Emperors, the subject of monarchy, dictatorship, autocracy, and the struggles between reformers and those who have a vested interest in preserving the old order of things.
The cast is massive, and as well as having a significant overlap with I Claudius encompasses loads of familiar faces from British TV of the era, Doctor Who not least, and I shall endeavour to point these out as they come up.
One thing this series cannot be faulted for is the acting. Elisabeth is played by Diane "Sandbaggers" Keen, who is the main character for this episode. But by the time the characters of Franz Josef and Elisabeth return, in part four, they will be many years older and so played by different actors - a lack of continuity that distances this episode from the rest of the series, and this is the main reason I think it is the weakest link.
Of the three empires, Austria gets the least focus in the series. I think this episode could have worked better had the Austriancentric parts one and four been placed together, since the latter of these, Requiem for a Crown Prince, is one of the best of the series and Death Waltz does work well as a prologue to the events in that. But the episodes are arranged in chronological order so this was not to be.