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Welcome to Holy Smoke, the Spectator's Religion podcast. I'm Damien Thompson. On a frosty evening in December 1951, shortly after Evenson, the interior of St Paul's Cathedral resounded to a series of reports fired from a cult revolver.

Each shot resonated clearly for almost 12 seconds in the phenomenally

reverberant cathedral interior before fading below the threshold of audibility. The effect, though

startling, was curiously musical. With every shot fired, tones and overtones were amplified and distorted, ringing as they

reiterated throughout the dome, galleries and chapels, before gradually peering into silence.

What on earth was going on? Well, the person to tell us is Dr. Fiona Smith, a historian of art

and science specialising in acoustics, because

that description is taken from the preface of her fascinating new book, Pistols in St. Paul's,

science, music and architecture in the 20th century. I caught up with her earlier and asked her,

why were pistols being fired in St. Paul's Cathedral?

Thank you, Damien, and thank you for that question.

It's a loaded one with absolutely no pun intended.

The pistol fire was an acoustic signal.

It was a demonstration for the press as well as a test.

The pistols were fired in order to measure the response of the building

to a particular signal and to gather information about the acoustics, to gather technical and

scientific information, but also to make a bit of a splash and to let the world know what exactly

was happening in acoustics at the time.

And it was actually rather important in 1951 to know how sound travelled through buildings,

...