How do I avoid the Dragon while taking King Foltest along with me in the Prologue of The Witcher 2?

In the prologue, just after the first meet with the Dragon, there's a section where Geralt is supposed to (drag?) King Foltest across the walls.

How do I avoid getting maimed by the dragon? The first pass is easy, the second pass (just after the dragon breathes fire) is were I'm getting stuck at.

The tutorial mentioned hitting some button, but I'm getting frustrated by this

Make sure that you keep running down. Don't let go of that key.

The game is prompting you to press the right mouse button to dodge into cover from the dragon's fire. You'll notice the icon appear near the bottom of the screen; press it as soon as you can so you don't die, then continue running.