St David’s Day took me to Westminster Cathedral, to see the mosaic of St David that was blessed by the Pope last year. Westminster Cathedral is one of the wonders of London. The Byzantine style may have been chosen to avoid rivalry with Westminster Abbey, and a brick cathedral could be built far more quickly than a stone one. All the rose-red fabric, bar the last 50ft of the campanile, had been finished by the architect J. F. Bentley’s death in 1902, a mere eight years after he began the design.

The enrichment of the interior has taken longer. Strangely, the brickwork here is almost black-perhaps from incense and candle smoke. But glittering mosaics, which a priest described to me as ‘soothing and serene, yet exhilarating’, are slowly covering the walls.

I had always thought St David was known as the Waterman because he mortified his flesh by praying in water, but the Welsh artist Ifor Davies shows him with a beaker, showing he only drank water (bad enough, you might think).

The work, largely made by Tessa Hunkin of the Mosaic Workshop, shows that the art of mosaic-making is far from dead-and just as well: the present Archbishop of Westminster, Vincent Nichols, has set his mind on completing the domes.