The first wedding dress is for the photographs, the church and history. The second is for the evening itself. At royal weddings the gap between the two is wider than it looks - and it is the second dress that says more about the bride than the first.

In 2011 Kate Middleton swapped Sarah Burton's dress for Alexander McQueen for another model by the same designer - satin, sleeveless, with a pearl-trimmed belt and a small angora bolero. The same year Charlene of Monaco chose Giorgio Armani for the evening: silk gauze, an illusion neckline and a pleated skirt.

In 2018 Meghan Markle went in an entirely different direction - Stella McCartney, a clean line, a bare back, not a single embellishment. With that she sent a message worth more than any statement: the first dress belonged to the institution, the second was hers.

Charlotte Casiraghi chose Chanel haute couture that same year, with a halter neckline and a central slit. In 2015 Beatrice Borromeo went for Armani, with a double cape of silk and tulle. Both are examples of something rarely said out loud - the Monegasque school of dressing is freer than the British one, because it does not carry the same weight of protocol.

The two most unexpected choices stand apart. In 2021, in South Africa, Lady Kitty Spencer wore Dolce and Gabbana - pale blue tulle with hand-embroidered pink flowers, closer to a fairytale costume than a wedding dress. And in 2013 Madeleine of Sweden wore the vintage dress once worn by Queen Silvia, with a large bow at the waist. No designer can buy what a choice like that carries.

The rest stayed within the lines: Eugenie of York in champagne-coloured Zac Posen, Sofia of Sweden in lace by Ida Sjostedt, Sassa de Osma in Lima in a bias-cut dress with a tiara of natural wheat ears.

Here a second outfit has long been the rule rather than a novelty - the bride changes for the dancing and nobody blinks. The only difference is that at royal weddings that second dress later becomes a subject of analysis, while here it stays in the album. Whenever somebody opens that album thirty years on, it is the second photograph they will linger on - the one where the bride finally looks like she is enjoying herself.