Ten kilograms. That is what the dress weighed in which Alix of Hesse married Nicholas II on 26 November 1894 in the Grand Church of the Winter Palace, having become Alexandra Feodorovna. White silk with silver motifs, an enormous train, a ceremonial mantle of gold brocade lined with ermine.

The veil was English lace from Honiton, Devon - the same worn by Queen Victoria, her grandmother. The jewellery came from the crown, with 475 carats of stones that once belonged to Catherine the Great. That is a quantity that stops being clothing and becomes an endurance exercise.

And now the part that makes the whole story different from any other royal wedding. The ceremony took place twenty-five days after Tsar Alexander III died, on 1 November 1894. Twenty-five days. No celebration, no splendour, none of those gatherings the Russian empire staged when it wanted to be seen. Nicholas later wrote that he had to summon all his strength not to break down, because his father was not there.

So: a young woman in a ten-kilogram dress, in a church full of people in black, marrying a man who became tsar three weeks earlier and is prepared for none of it. The story of a falling empire is usually told from the end. Here the beginning already contains the whole tone.

Alexandra broke with tradition - she did not give her wedding dress to the Church as custom required, but kept it. That dress survived the revolution and is kept today in the Hermitage. She and her family were shot by the Bolsheviks on 17 July 1918 in Yekaterinburg.

The fabric remained, and not one of the people who wore it came back. That is the point museums rarely write on the plaque beside the display case, even though every visitor feels it: you look at an object while thinking about how little is left once everything else has gone.