10 Harry Potter Moments You Never Knew Were Improvised

Now, this one's a double-dipper.

With Voldemort (or at least his memory) defeated at the conclusion of Chamber Of Secrets, Harry and Dumbledore (Richard Harris) gather in Dumbledore's office for the traditional post-action debrief, and to hear an incensed Lucius Malfoy deliver his closing sneers while Dobby watches on in fear.

Seeking a way to have the final word, having been subtly dressed down by Dumbledore, Jason Isaacs ad-libbed the line 'Let us hope Mr Potter will always be around to save the day', without telling a soul what he had planned.

Always quick off the mark, the young Daniel Radcliffe retorted, 'Don't worry, I will be.'

And the crowd go wild.

That's right: twelve-year-old Radcliffe improvised the response on the spot - to the shock and awe of the cast, crew and eventually us, the adoring fans. And it just feels right - for the character, for the series, and for the moment, in what is one of the most memorable exchanges of the entire film.