It has become traditional, when a new series of Game Of Thrones lands among us, to herald its arrival with stories underlining its unrivalled status as the most pirated programme on TV.

Sure enough, this week, as fans counted down the final days to the fifth season of HBO's huge, hairy fantasy hit, the figures came rolling out: between February 5 and April 6 alone, more than seven million episodes were illegally downloaded- practically double the number of downloads during the same period in 2014.

Of course, the cold fact is that if the trend for grabbing the show for free continues, it has ramifications for the ability and willingness of HBO, or anyone else, to attempt to produce programmes on this scale in the future. For the moment, though, Thrones itself is simply thriving on it.

The series was originally hyped as "The Sopranos In Middle Earth." But Thrones never really seeks to use the opportunities long-form TV presents to go deep in the way of a Sopranos or a Mad Men: it's more like Tolkien collaborating with Lucrezia Borgia on a psychotic new gothic fairy tale version of Dallas, with help from the Playboy Mansion. But what it lacks in depth, it more than makes up for in sweep and swagger. From the first, taking cues from Peter Jackson's Lord Of The Rings movies and a little of the dirt of HBO's groundbreakingly gamey western, Deadwood, the programme ushered in an epic muscularity that was new to TV. As the fifth series begins, it just looks and feels bigger and more confident than ever.

How confident? Well consider this. The last season ended on a tide of slaughter, betrayal, banishment and exile that left a world in the balance, and left fans gagging for what comes next. So, of course, the eagerly awaited new series opens with... faces we've never seen before.

Actually, we do know one of these people well, it's just we've never seen her like this. We are deep in a muddy green wood, following two young girls (to prevent spoilers we can't tell you who they are) as they journey to visit a rumoured witch in her ragged hut. There are prophecies made which we begin to recognise as having already occurred, and then suddenly we are back where we left off last year, as the episode begins to flit from place to place, catching up with the scattered cast.

In King's Landing, a new religious sect is on the rise, while the final preparations have been made for the funeral of Tywin Lannister, the awesome patriarch cataclysmically crossbowed on the toilet by his son, Tyrion -the true, reluctant anti-hero of the saga, who has been smuggled away by ship, locked in a crate.

North, at The Wall, Jon Snow and the Night's Watch wait to hear what price would-be king Stannis will demand for saving them from massacre by the wildlings. Out in the plains, female knight Brienne continues her increasingly hopeless quest to find the lost Stark girls. And far away, across the sea, the possible future queen Daenerys Targaryen must deal with stirrings of revolt - not to mention three recalcitrant dragons.

We don't catch up with everyone yet. There are faces notably absent from the opening episode, and - confidence, again - this series takes its time setting out its stall over the first four weeks. While it moves relatively slowly, however, as the pieces are drawn together, the pace, the dread and the thrill mount with each episode.

This is a watershed season. Game Of Thrones faces its biggest challenge now, in that it has caught up with the source novels it comes adapted from, and is beginning to outstrip them. The author, George RR Martin, began his series back in 1996, is still working on the sixth book, and has speculated he might need eight to wrap it all up. HBO has announced it will not wait, and that the show will end long before Martin's books do. For some fans this could be an irreconcilable dilemma. But for those who watch the series on its own, it might prove to be the best thing that could have happened to it.

The TV show has been faithful to Martin, but has already started to deviate from his novels. The pace and extremity of the deviations is accelerating now, as the writers ease their shackles, hone in on their own conclusion, and, crucially, take inspiration from the way an incredible cast of actors have made Martin's characters their own. What could have been an insurmountable problem has become an opportunity, one that has the potential to re-energise the programme... or derail it. The biggest thrill about this series is that it sees Game Of Thrones moving, with an increasingly cinematic strut, into uncharted territory. Here be dragons.