The Great Hall was a physical set at Leavesden Studios, lit by nearly 400 floating candles hung on wires. The enchanted sky above was added digitally, but the flagstone floor was real York stone.
The Patronus Charm conjures a guardian of pure positive energy shaped like an animal that reflects the caster's personality. Harry's stag mirrors his father's Animagus form.
Across eight films the production destroyed roughly 160 pairs of Harry's round glasses and about 70 wands, mostly during stunt and action sequences.
Ollivander's wands contain a core of phoenix feather, dragon heartstring or unicorn hair. The wand's loyalty can shift if it is won from its owner in combat.
The train is GWR 5972 Olton Hall, a genuine steam engine repainted crimson. It ran on real track in Scotland, including the Glenfinnan Viaduct.
Dementors drain peace and joy from anything near them, leaving only the worst memories. Chocolate helps because it restores warmth after the cold of their presence.
The barrier scenes were shot between platforms 4 and 5 at King's Cross Station, because the real platforms 9 and 10 lacked the arched Victorian brickwork.
