Whenever I pick up a book who's plot involves time travel, I get a bit wary - I read in constant fear of a paradox ruining the story for me, as I'll invariably pick it apart, proving that such-and-such couldn't happen because so-and-so did this, that or the other. It's rare for an author to pull it off without writing him or herself into a corner, but Ian Watson has accomplished it with flair. Not content with planting a first Century Roman Centurion in modern Britain, he also manages to delve deeper, adding politics to the mix and making it an integral part of the plot, even managing to show substantial comparison between events witnessed by the Roman and those happening in modern-day Ireland.
He doesn't faff around with phoney scientific explanations for the sudden appearance of a man from the past either - he gives the reason, but doesn't offer up scientific theory, which makes a refreshing change and also means that as science progresses, there will be fewer holes picked in this novel than in some others (hurrah!).
This would have been awarded 9/10 but for the ending which was rather abrupt and felt like a bit of a cop-out - it felt unfinished, like Watson had more to say but was edited in the final chapters, so a point is retracted. Still, what remains is an intense political thriller with terrorists and a Roman soldier in tow and it's a while since I've read something of this kind that was so good. It's well worth a look.