This transfer of Neil Simon’s three-act play about couples in crisis comes with Broadway’s famed levels of audience appreciation, perhaps unsurprisingly given that New York royalty is headlining. The whooping begins at the sight of an empty set. Decibels rise when Sarah Jessica Parker walks on. Matthew Broderick’s entry stirs more hoopla. One woman in my sight-line holds up a glowing phone to secure her brazen memento, 15 minutes in. Parker has already asked an audience member at a previous show to put away their phone, mid-production. Ushers zip up and down the aisles, clearly hoping to prevent another such misdemeanour. Never mind the comedy on stage, this is a celebrity circus. Even costume changes get audience oohs and aahs. It seems oddly disproportionate because, as exciting as it may be to see Sex and the City’s Carrie Bradshaw on stage, the production is flat and forgettable, not testing either actor’s seasoned skills on the boards (though this is Parker’s debut in the West End). That is a shame because there is something thrilling about its premise: for Parker and Broderick, who are married, to play three different 1960s-era couples living in marital disharmony, each dramatising their unspent desires and disappointments in the same swanky seventh-floor hotel suite. What truth and tension can they bring to Simon’s romcom gone awry? Not much. Under the direction of John Benjamin Hickey, it feels strangely like Parker and Broderick are saying lines rather than assuming roles. The first, most sober act features a couple, married for over 20 years, on their wedding anniversary. She is annoyingly ditzy, he is pompous and annoyed. Parker puts more energy into it but Broderick is oddly stolid. When an affair is uncovered, there is some ice but no fire. The tone stays that of a breezy comedy of manners with no real pain glimpsed within it, however briefly.