London theatergoers got a horrible shock when the ceiling of the historic Apollo Theatre caved in during a performance Thursday night. A large section of the plaster ceiling fell on the audience, damaging the auditorium's balcony and injuring a reported 76 people.

Seven people were severely hurt, but thankfully all victims left the scene conscious and breathing. It's too soon to be sure what caused the accident at the Edwardian theater (there's no sign of criminal damage) but the roof may have been weakened during a heavy thunderstorm that saw 15 percent of London’s usual (substantial) December rainfall within a single evening.

The accident is likely to spark emergency surveys for all of London’s historic theaters. While the Apollo's management would no doubt have acted fast had they known that anything like this could possibly happen, there have been warnings about the dilapidation of London theaters for years. Having a historic theater district may be a blessing, but it comes with a burden of care that profits don't easily support. All but two of the 40 theaters in the West End district – London’s equivalent to Broadway – were built before WWII, and these ornate, charming buildings are increasingly showing their age.

Actually, they were largely quite flimsy to start with, and for good reason: the buildings were never expected to last. In the days before electric light and proper fire regulations, London’s theaters were notorious for burning down. The city's Opera House, for example, was destroyed by fire three times during the 19th century. The theaters that survived still needed regular remodeling not to fall out of fashion, so construction had little reason to be anything but cheap.

Completed in 1901, the Apollo Theatre was built slightly after the era of regular infernos, but it still shares many inconveniences left over from a different time. Crusted with elegant stucco statuary on the outside, it nonetheless has cramped public areas and a balcony so steep (the steepest in London, in fact) that sitting there demands a complete lack of acrophobia.

When theater profits started falling in the 1940s, there wasn’t much money around for refits for buildings constructed along these lines. New construction trailed off (at least in the West End) and the playhouses that stayed open largely had to patch up what they had. This drying up of audiences also affected the choice of plays for production. Premieres of serious drama gradually moved from the West End to London’s state subsidized theaters, leaving the former to concentrate on musicals and light comedy. This shift ended up having lasting effects, and indeed still today many of the West End’s most critically acclaimed productions only transfer there after successful runs at places like the National Theatre or the Almeida. This has put West End theaters in a complicated position. They are housed in fragile, historically protected buildings and carry on a venerable, world-famous tradition worthy of preservation. They are also associated with commercial productions (often without great prestige) that are aimed primarily at making healthy profits. With ticket prices high even by European standards, West End theaters don’t really cut it as obvious targets for state support.

Theater owners haven’t accepted their aging buildings' decay quietly. Ten years ago, there was a high-profile campaign to find £250 million from Britain’s National Lottery to renovate London’s historic theaters, rightly arguing that the buildings were culturally valuable, good for tourism and worthy of preservation for their beauty alone. The money never came through, and right up until this year there have been dire warnings of chronic underinvestment in West End theater. To make up for this, London theaters themselves have slapped a "restoration levy" on ticket prices. Typically for the West End, the Apollo Theatre charges an additional £1 per ticket for just that purpose.

There’s evidence that some of the money levied is indeed being plowed into restoring theaters, but critics have complained about a lack of transparency that makes it impossible for audiences to know exactly how much of the charge is going into restoration. Critic Michael Billington even complained that the levies were like inviting guests to a dinner party, then charging them money for the dishwasher.

It's too early to say what caused the collapse at the Apollo last night, or whether the theater's parent group has spent the revenue from its levies wisely. But the incident is likely to stir up some serious soul searching about exactly how London’s West End theaters should be preserved, and by whom.