Sitting on a bench in the Real SFX workshop – where the physical special effects of the show are prepared – are the remnants of an exploded Dalek.
The singed bottom half houses a charred mess of wires and circuit boards in place of its guts. Danny Hargreaves, the physical effects supervisor on the show, explains that a “soft section” of the Dalek was made out of biscuit foam, a kind of brittle, resin-based substance that’s very soft and crumbles like a biscuit. Normally, boards of it are used to help insulate walls. But for Doctor Who it’s typically painted to look like brickwork and gets blasted out of air canons to mimic the flying debris from explosions.
“It took a couple of weeks to construct and fabricate the shell,” says Danny.
“We then put three explosive charges in there. This is the part where we have to know our explosives. It has to blow up a very particular way.
So we had one at the base, one in the middle and one in the head, and set them off in a quick sequence. We used petrol as well so it burned for a little while after.”
To Danny’s credit, the half-Dalek doesn’t look that damaged for something that’s taken such a beating. “We don’t actually try to damage its structural integrity,” he says. “We want maximum effect with minimum force. The biscuit foam is very soft so I’d only need a very small charge to blow that apart – what we call a theatrical maroon – and then we just focus on the fireball.”