The CG elephant was a last minute replacement because the real baby elephant suddenly died. A deceptively small part, yet the mechanics involved in getting an elephant convincingly up a flight of stairs and into bed were not easy under the time constraints.

The film's climactic vfx sequence takes place in a field, with Nanny McPhee standing in its center magically guiding the vital harvest of barley up into the air, where it swirls into a huge flock of starlings, forming into a series of creatures before bursting like a firework display and descending on the stunned humans below. Under the leadership of CG Supervisor Chris Lawrence, a team of six created the magical harvest as an animation-driven flocking simulation within Houdini.

"The magical harvest was always storyboarded, but nobody knew what it looked like," Manz suggests. "I think the final storyboards for that were five weeks before the end of delivering the film, so that was a huge undertaking. We had to come up with a way to efficiently simulate all of that flocking. We wanted to give the director the ability to direct the animals' shapes, so we came up with the system where they could direct an animated creature and we turned it into barley afterwards. The animals were animated in base particles with simulation dress up. The brief for them was that they would look like flocking starlings, so we found reference for them and the almost unreal shapes they create in the sky for real. I would say that was the most challenging sequence, particularly as that's the climax of the film."

Bill Desowitz is senior editor of AWN & VFXWorld.