LONDON — Theater here is consistently shocking these days. Not because of what’s transpiring on the city’s stages, but because of what’s happening in the seats: Mostly maskless London theatergoers seem oblivious to the ongoing hazards of the coronavirus.

It’s theatergoers in New York and Washington who are revealing the true stiff upper lips — if you could actually see them under their masks, which they wear as an absolute rule in most venues. Most of their London counterparts display no such discipline regarding public safety, ignoring en masse the requests of theater management to strap on masks while seated.

Then again, on my recent visit, there was virtually no London theater, not even the esteemed National, that bothered to check for proof of vaccination, a fundamental requirement on Broadway and elsewhere in the United States. What makes this recklessness all the more appalling is that coronavirus numbers are on the rise in the United Kingdom and much of the rest of Europe. Which prompted this thought: Is it any wonder?

I spent two weeks in London last month, attempting to wind down from the whirlwind of an early fall of theater openings in New York and Washington — by seeing more theater. Yes, I am that kind of glutton for entertainment. The seemingly lackadaisical attitude across the city in hotels and restaurants, bars and the Tube made me uneasy and extra vigilant. The older gentleman next to me at the Royal Opera House in Covent Garden, the young couple at the Almeida Theatre in Islington, the mom with the two children at the Swan Theatre in Stratford-upon-Avon — all seemed to have taken their cue from a British government that has thrown caution into the Thames, at least with regard to safety protocols.

So triple vaccinated and religiously KN-95 masked, I intrepidly presented myself to ticket takers throughout the city, and beyond. London is of course an essential destination for lifelong theater pilgrims like me; I’ve come dozens of times since my undergraduate days in the ’70s.

On this visit, I sampled eight plays and musicals (plus the Royal Ballet’s “Romeo and Juliet” with an incandescent Francesca Hayward). It was an eclectic menu of bull’s-eyes and target misses that included the Almeida’s bracingly effective “The Tragedy of Macbeth” with the keenly well-matched James McArdle and Saoirse Ronan as the coup-minded couple. I also took in that play’s cultural polar opposite, a new musical version of “Back to the Future,” said to be bound for Broadway but that could just as easily head directly to a theme park near you.

Along the way, there were stops at the National Theatre for two play revivals: a moving production of “The Normal Heart,” Larry Kramer’s masterwork about the ravages of AIDS and American officials’ catastrophically slow response, and Ayub Khan Din’s “East Is East,” an unevenly staged dramedy about generational disconnect in an Anglo-Pakistani family. (“The Normal Heart” unfolded as astonishingly timely, with a deeply affecting Ben Daniels as Ned, the story’s rabble-rouser, declaring, “I am trying to understand why no one wants to hear that we are dying.”)

The highly regarded Donmar Warehouse offered a relentlessly grim dystopian drama, Cordelia Lynn’s “Love and Other Acts of Violence,” and the Royal Shakespeare Company served up “The Mirror and the Light,” a lackluster West End sequel to its “Wolf Hall” series about the life of Thomas Cromwell in the court of King Henry VIII. (That production at the Gielgud Theatre was the only one to verify vaccination.)

The RSC, minters once upon a time of the hit musical “Matilda,” also accounted for my emptiest experience: “The Magician’s Elephant,” a new musical, in its historic Stratford-upon-Avon home base, adapted from a children’s book by Kate DiCamillo. Overproduced and undernourishing, the show is a mishmash of dispiriting conceits, revolving around an unhappy young man and an abused pachyderm. At least in Stratford there was the grave of Shakespeare to pay homage to.

Speaking of Shakespeare: His work provided for one of the two best evenings of the trip; the other made possible by Jane Austen. “The Tragedy of Macbeth” at the Almeida is directed by Yael Farber, who staged at D.C.’s Shakespeare Theatre Company the searing “Mies Julie,” a South African riff on August Strindberg’s “Miss Julie.” At the Almeida, Farber masterminds a modern-dress “Macbeth” centered on the notion of a young Lady Macbeth, fashionably swathed in white by Joanna Scotcher, who is aware of her charms but unprepared for the magnitude of malevolence she unleashes.

Farber’s Scotland is a domain of kilted soldiers with automatic weapons who nevertheless are vulnerable to the self-assured entreaties of Ronan’s iron-willed Lady M. The banquet scene — in which the ghost of murdered Banquo (a potent Ross Anderson) turns McArdle’s wavering thane to jelly — is beautifully handled. At a microphone, Ronan’s Lady Macbeth tries desperately to salvage the evening — “The fit is momentary; regard him not” — as Macbeth falls apart. As a cello played by Aoife Burke provides mournful underscoring, a spectator gets rewarding insight into the breakdown of a tragic coupling.

The impact of the trip’s other theatrical highlight was far more buoyant: a witty soufflé of an entertainment titled “Pride and Prejudice (sort of).” Written by Isobel McArthur and performed by McArthur and four other actresses, the comedy at the Criterion Theatre revolves cheekily around the servants in the households of Austen’s novel. Like Tom Stoppard’s minor “Hamlet” characters grabbing the spotlight in “Rosencrantz and Guildenstern Are Dead,” the housemaids are the stars here, portraying all the characters.

Over two acts and more than 2½ hours — a luxurious length that might merit a judicious trimming — the actresses take us on a merry jaunt through the novel, with a few pop tunes thrown in. The other performers, uniformly dexterous and winning, are Tori Burgess, Christina Gordon, Hannah Jarrett-Scott and Meghan Tyler. Under the smart direction of McArthur and Simon Harvey, the cast conjures all that is piquant and joyful in Austen’s work; you can imagine Jane getting a kick out of the antics. It reminds you how refreshing the results of an exuberant brainstorm can be.

Finally, on one of my last days in London, I approached with a mix of expectation and trepidation the stage version of “Back to the Future” — the anxiety fueled not only by that London aversion to masks, but also by my growing allergy to musicals based on brand- name movies. This one had a couple of appealing come-ons, namely, the casting of Roger Bart as Doc Brown, the wacky scientist made famous by Christopher Lloyd in the movie franchise. Then there was the snazzy DeLorean, the storied car in which Marty McFly travels back in time for some high jinks involving the younger versions of his mom and dad.

John Rando directs a mostly British cast in this overcaffeinated exercise, crammed with references to the movie and a passel of songs by Alan Silvestri and Glen Ballard that don’t make a memorable dent in the consciousness. Bart is himself stuck in maximum overdrive, in a performance that is all joke-milking and mannerism. At least the car shifts gears efficiently, rising above the crowd through the magic of designers Tim Hatley, Finn Ross and Chris Fisher — and outshining the less impressive gewgaws of this wholly ordinary musical machine.