Hedgehog entering garden sniffing
UPDATE: When I first posted this video, I captioned it "Hedgehogs have a keen sense of smell and might be trying to find food or a mate -- spring is in the air!" However, there seems to be more to it.
After sharing experiences with other hog watchers, this sort of behaviour seems common just after entering a new area having gone through a confined space. It would seem that as prey animals, a behaviour has evolved such that hedgehogs will sniff for possible predators (primarily badgers) when entering a new space knowing that they could turn around and return through the confined space that might stop a badger following them.
This makes a really good argument for hedgehog highways will holes big enough for our stripy friends to walk though but too small for our stripy friends to follow!