It's not unusual for the great and the glamorous to be gracious and charming, but it's rare for them to be genuinely comfortable, warm and genial when conversing with a crowd.
Yet Sir Ian was all this at the weekend, and mischievously funny to boot.
His one-man Q&A and recitation show is a mutual love fest between actor and audience. On Saturday, the audience sang him Happy Birthday (a day late for his 72nd); after, he posed for pictures with fans.
Did he encounter any snobbery for starring in comic-book adaptation X-Men? "No, because the real snobs didn't know I'd done it," he quipped.
What did he think of Kiwi men? asked a male voice. "Stand up!" (subtext: let me look at you) came the challenge in reply.
He amused with stories of his knighting, but he also disclosed moments of frailty and self-doubt, such as once drying up onstage for a whole scene with Judi Dench (who then said his lines as well as her own).
His recitations were a well-chosen mix of the well-known and probably-never-heard-before. Many emphasised the importance of theatre in presenting complex themes, and the worries of ageing.
The show started with Tolkien himself - the entertaining dramatics of Gandalf's battle with the Balrog ("fly, you fools!") - before a northern-accented Wordsworth, and a Victorian poem from Gerard Manley Hopkins.
The second half was dedicated to serious Shakespeare - including a whispered "once more into the breech, dear friends!" from Henry V and homoeroticism from Coriolanus. The jokey encore involved audience members cluttering up the stage as dead French soldiers.
What a real treat.
What: Ian McKellen On Stage With Shakespeare, Tolkien and You.
Where: Q Theatre.
When: Saturday and yesterday.