The answer is “Dame Judi Dench.” The question? Name one British character actor of note who hasn’t made an appearance/ collected a check from the “Harry Potter” movies. With the news that the great Bill Nighy will play Rufus Scrimgeour in the two-part finale to the series, that short list just got a bit shorter.

A series that has gone through Great Brits like butter beer through a Weasley will someday be required viewing for anyone writing a book on British Isles acting.

“Harry Potter and the Half-Blood Prince” has Oscar winner Jim Broadbent in a featured role as Horace Slughorn, potions professor.

Broadbent joins Imelda Staunton, Kenneth Branagh, Fiona Shaw, David Thewlis, Brendan Gleeson (MadEye Moody here, an “In Bruges” co-star) Emma Thompson, Julie Walters (Mrs. Molly Weasley), Ian Hart, Helena Bonham Carter, Richard Griffiths (Uncle Vernon Dursley was in Venus, “The History Boys”), Miranda Richardson, Gary Oldman, the diminutive Warwick Davis (of “Willow,” he’s Professor Flitwick), Shirley Henderson (Moaning Myrtle), Jason Isaacs, Julie Christie, Timothy Spall (Wormtail in the “Potter” pictures, the Queen’s henchman in “Enchanted”), Richard Harris, Michael Gambon and John Hurt.

And you just knew they weren’t wasting Alan Rickman (Severus Snape) on a bit role, even if you had to wait six films to see him step out of the shadows. Or into them.

Gathering them all for one big cast photo would empty U. K. film sets and the West End stage in one fell swoop.

The shorter list is “Who’s been left out?”

There’s Vanessa Redgrave. Ian Holm (“Lord of the Rings”) and Ian McShane (“Deadwood”) never did a Potter movie. Nor did the great Derek Jacobi (“Henry V”) or Patrick Stewart.

Or the tall, dashing Ciaran Hinds of “Calendar Girls” and “Munich.” But wait. He’s Abeforth Dumbledore in “Deathly Hallows,” due out in 2010 and 2011, joining a ledger so illustrious as to make the phrase “all-star cast” superfluous.