Harry Potter’s Aunt Petunia is half-buried in the Earth. But hey, who isn’t?

That, I’d say, is a fair reduction of Samuel Beckett’s 1961 Happy Days, a not-quite-monologue for a middle aged woman who is stuck in a rut, though really it seems to be more of a pool of slow-acting quicksand. And the woman playing The Woman — actually, she has a name; it’s Winnie — in the National Theatre of Great Britain production making a brief stop at the Kennedy Center this week, is one Fiona Shaw, who has a list of stage and screen credits as long as The Complete, Unedited Manuscripts of J.K. Rowling, but is now probably most famous for her role in the Harry Potter films. C’est la showbiz.

Reuniting with her frequent director Deborah Warner, she’s taken on what must be one of the toughest roles ever penned, a highly repetitive, 80-ish minute existentialist rap for a woman who can’t move. “What is that wonderful line?” Winnie asks over and over again, as if her situation can be tidily summed up by a familiar aphorism — one of many clues here that Beckett doesn’t consider her predicament grotesque, or at least no more so than ours. Her husband, Willie, is there, too, but only for intermittent groans, cries, and applications of Vaseline. “You’re not the crawler I gave my heart to, dear,” Winnie sighs, her spirits seeming to sag only when she remembers that she’s married.

The answer to “what can even a great actor possibly do with such constraints,” turns out to be, “quite a lot.” But don’t sit in the back half of the house, since, without giving anything away, her mobility is further impeded in Act Two. As the margins of Winnie’s words shrink, she maintains her cheerful perspective on the routine, though of course every day is not just like the next, because each day we’re a measurable step closer to oblivion. Anyway, you probably already know whether this is your cup of existentialist despair. I mean, tea.

Pictured: Fiona Shaw counts her blessings in Samuel Beckett’s Happy Days.