Sir Christopher Wren would have liked the interior of St Paul’s to have been richer than it was when he left it. He had hoped to cover the piers in coloured marble. Rather than Thornhill’s grisailles beneath the dome, he would have gone for mosaics.

A mosaic scheme was finally erected, but only in the Victorian period, and the jury has been out ever since. I was reminded of these controversies last Sunday, when I sat beneath the dome, listening to an organ recital by Greg Morris. Sound rose into the upper reaches of the architecture like incense.

From Monday to Saturday, St Paul’s Cathedral is not somewhere to visit lightly-the £15 entrance fee deters popping in. But the authorities make up for it on Sundays, when the doors are thrown open, the cash tills fall silent and, for good measure, an organ recital is laid on, for which one pays nothing. Admittedly, the effect of the instrument wasn’t quite what I’d expected.

Low notes on the organ in our church can practically be measured on the Richter scale; your bone marrow and viscera seem to quake. There are too many spaces for sound to escape at St Paul’s, and reverberation adds extra parts to a fugue. But I’m not complaining. It was glorious.

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