An example of Radzinsky's slightly fanciful speculations. This passage concerns the arrival of the first secret "Officer Letter" in the Ipatiev house:
"This is how the letter promising them escape appeared. It was signed: 'Prepared to die for you, an officer of the Russian army.' Oh, how Alix likes this signature. Her migraines are but a memory. She is once again the old spitzbube. Yes, it has come to pass. They have come. They have not abandoned their tsar! Good Russian people! They are prepared to liberate their emperor. The holy man has sent the family a 'legion of angels.'
"She begs Nicky to reply. As always, he calmly agrees."
~The Last Tsar, pg 318
To my knowledge, there's no record of how Nicholas and Alexandra reacted to the arrival of the first letter proposing an escape plan. Alexandra's diary doesn't mention it at all. So it appears that Radzinsky invented the notion that Alix "likes this signature" or "begs Nicky to reply," and that "he calmly agrees." Sure, these reactions are all consistent with what we know about the imperial couple's personalities, but no matter how well Radzinsky knows his subjects, the fact is that NOBODY really knows how the tsar and his wife reacted to this letter. To my way of thinking, that means this passage is technically historical fiction. The scene he's created is possible, maybe even probable, but it's NOT non-fiction.
Radzinsky's done a heap of research in Russian archives and has had access to formerly classified information. As a result, he seems to feel a deep intuitional, even mystical connection with Nicholas and Alexandra. Frankly, I think that's pretty nifty, and I think his extensive research probably has given him great insight into the imperial family. However, I still want to know when the information he presents is derived from fact, and when it's coming from his own instincts.