How It: Welcome to Derry's genius Pennywise risk pays off – and makes it scarier than the films

**Warning – It: Welcome to Derry spoilers ahead.**

If the opening episode of It: Welcome to Derry didn't leave you reeling, you might be dead inside.

I'm not being dramatic. The opening episode of the long-awaited prequel doesn't just throw us in at the deep end, but holds us under the water until we're gasping for breath.

The gory first instalment introduces viewers to the ill-fated Matty, who's trying to escape an abusive home environment. But, after he's picked up from the side of the road by a strange family, the showrunners hold nothing back as they force Matty (and us!) to witness the birth of a demonic baby, amping up the body horror as Matty is snatched before our very eyes.

After Matty's classmates (AKA the current Losers Club) witness strange and nightmarish happenings, things go from bad to worse with the movie theatre scene – a brutal sequence that sees most of our new Losers Club toyed with and murdered, as our good friend, the demon baby, makes its gruesome return.

Of course, we know whose handiwork this is. Despite manifesting in a different form, we know exactly who feeds on fear in this way. But, then, why don't we ever see the dread creature that haunts Derry, Pennywise?

In fact, the showrunners have confirmed that we won't see Pennywise as we know and hate him for some time. Of course, his presence is felt all over the first episode, but for those hoping to get a glimpse of the Dancing Clown this early on, you might be disappointed.

In my book, though, that's the best decision that could have been made. In hiding Pennywise from us, the showrunners master an age-old rule of horror movie magic: hiding the monster. Any horror fan will be familiar with the rule, which has been used in thrillers and horrors across the ages, from Jaws to Jurassic Park to the Blair Witch Project to Paranormal Activity to A Quiet Place and beyond.

In short, hiding the monster allows our imaginations to run free. Nothing the filmmaker could ultimately show us on screen could match up to the horrors we could imagine.

As horror researcher Mathias Clasen recently told RadioTimes.com, hiding the monster "allows us to build a model in our own mind that is worse than anything that you could put on a screen. The human imagination is a horror director, and the imagination very quickly runs to worst case scenarios".

"That's just the way that the human imagination works, because one of its functions is to forecast, is to kind of create simulations of possible futures, very often running toward worst case scenarios," he added.

"So the human imagination can produce ideas and images that are way scarier than anything you can see on a screen, also because it's personal. The imagination takes elements from your own biography and combines it with whatever stimulus is setting it off and and creates your own worst nightmare."

Doesn't that actually sound a lot like what Pennywise himself does? In keeping the Dancing Clown off-screen, the filmmakers have, purposefully or not, emulated the impact of the very villain they're teeing up in a genius move.

Just as Pennywise haunts the Losers Club on screen with their worst nightmares, feeding off of their fear, Andy and Barbara Muschietti and co have done the same to us, forcing us to bring our own fears to our viewing experience.

But how It: Welcome to Derry hides the monster is obviously very different to our previous examples, all of which rely on the unknown. We've all seen the It films, and we're all very aware of what Bill Skarsgård looks like as Dancing Clown.

As terrifying as it might be, a hint of that horror could be toned down with him being so familiar.

Now, the terror is preserved in not knowing how or when he's finally going to appear. Throughout the first episode of It: Welcome to Derry, Pennywise is a looming and very real presence, but one you can never quite grip onto, much like a balloon floating away in the wind. Our anticipation is heightened. He's around every turn, in your periphery at every moment – simultaneously everywhere and nowhere, only to appear when you least expect it.

That's so much more effective in a series than it would have been in a film, too. It's the ultimate slow-burn, as we could be waiting weeks for Pennywise to finally spring into action.

In the first episodes of Welcome to Derry, Pennywise haunts us not in his Dancing Clown form, but in the form of children's nightmares, filling them with fear as he effectively fattens up his meal, before eventually showing himself only when he's good and ready to feast, in a chilling and even theatrical scene that is sure to delight viewers (I promise, he's worth the wait).

Hiding his most familiar and recognisable form away for so long was a huge risk for the showrunners. Due to the nature of the story, he and the town of Derry are some of the only constants in the franchise, with the cast of characters changing every time. The Dancing Clown is synonymous with It, so much so that I'm surprised hiding him hasn't gone badly wrong.

It allows us to learn much more about the characters by seeing their worst nightmares come to life, and indeed about ourselves as we imagine every horrible way he could manifest before we finally see him in action.

As he famously declares, he is every worst nightmare you've ever had – and this might be the worst of them all.

New episodes of It: Welcome to Derry are released weekly on Sky Atlantic and NOW.

Add It: Welcome to Derry to your watchlist on the Radio Times: What to Watch app – download now for daily TV recommendations, features and more.

Check out more of our Sci-fi coverage or visit our TV Guide and Streaming Guide to find out what's on. For more TV recommendations and reviews, listen to The Radio Times Podcast.