Rupert Grint (aka Ron Weasley) and Emma Watson (Hermione Granger) aren’t among that team today — they’ve headed north for an outdoor location shoot — but the boy wizard himself, Daniel Radcliffe, is present for duty in the place he’s called his second home since before he was even a teenager (he turns 20 next month).

Radcliffe’s not in this scene, but he’s happily watching what Jim Broadbent, who makes his Potter debut in the Half-Blood Prince as Horace Slughorn, does with his several go-throughs.

Slughorn is greeting guests, including Luna Lovegood (played by the wonderfully eccentric Evanna Lynch) dressed up like a silver Christmas tree, and with each take Broadbent mixes it up — easy stuff for a veteran of his status.

‘‘I wasn’t in the first shot this morning but I went down to watch it just ’cos . . . I’m just interested in it and I want to see how other people act together. It’s about learning, for me,’’ Radcliffe says.

‘‘I like wandering round. Sometimes I go and play table tennis or I’ll read or I’ll play a computer game. But most of the time here I’m on set, so there is not a huge amount of down time.’’

By the time we wind our way out of the Leavesden maze, it’s dark outside and freezing. Radcliffe feels our pain. ‘‘The only problem with being here, especially during the winter months, is you wake up at six in the morning, you get in here at eight o’clock and it’s pitch black, and you leave at seven o’clock and it’s pitch black,’’ he says.

‘‘You don’t really get a sense of time passing ’cos you don’t see daylight. So that can be quite depressing.

‘‘But I’m perfectly happy to be here because I’ve been here more or less nine years. I’m so used to the place.’’

‘‘I don’t like the idea of just walking out of this place and never seeing anybody again,’’ he says. ‘‘That would be very sad.’’