"Bird's Custard is the brand name for the original powdered, egg-free imitation custard powder, now owned by Premier Foods. Custard powder or instant custard powder are the generic product names for similar and competing products. The product is a cornflour-based powder which thickens to form a custard-like sauce when mixed with milk and heated."
You want to watch a few more science programs, fuel-air explosions are worth watching. Better if you do them yourself though!
I was just reading the ingredients listed on the tin. Maize is also corn I think. But I don't want to create fuel-air explosions!