At first glance, the John Parker set for this excellent (potent pause) production looks merely 1950s realist. However - fittingly for a Harold Pinter play - not all is as it seems: the lamps suspended over the action are shaped like hand grenades. What we call "conventional" is shown to lead to dangerous, humorous and strange places.
An older, "simple" couple host a younger, sneering boarder (Joseph Rye) - surrogate son, object of desire or both? - who seems extremely worried when two mysterious strangers ride into town.
The Birthday Party can be variously read as a comic cautionary fable of post-war lobotomy culture; a dreamlike dissection of suburban paranoia, delusion and depression; an unravelling of outsiders clinging to norms; a post-Freudian observation of the topsy-turvy power dynamics of sexual and social relationships ... the list goes on.
Pinter doesn't pay cause-and-effect all the respect they're used to, nor does he close down options by tying up loose ends. Instead he leaves them lying around for us to pick up; a satisfyingly rich haul.
The darkly funny surrealism is all the more striking because it's played out in front of a portrait of the Queen; Pinter is Beckett in a drawing room.