Six kings and seven queens were among the 2500-strong congregation, the largest gathering of royalty, regnant and exiled, anyone could remember. As the sound of cheering outside the abbey rose from a rumble to a mighty roar, the rousing hymn, ‘Praise My Soul, The King Of Heaven’ provided the vocal backdrop to the entrance of the princess and the King. The young bride in her ivory satin Norman Hartnell gown held onto the arm of her father, who was dressed in the uniform of the Admiral of the Fleet. Directly behind them and three paces ahead of the other bridesmaids, in deference to her rank, Princess Margaret walked, alone.

The Archbishop of York had the right idea, but it must have sounded improbable when he told so much assembled finery – tiaras, top hats, long dresses, uniforms and robes – that the marriage was ‘in all essentials the same as it would have been for any cottager who might be married this afternoon in some small country church in a remote village in the Dales’.

After the service, the Duchess of Edinburgh laid her bridal bouquet – which had briefly gone missing at the palace while everyone was getting ready – at the Tomb of the Unknown Warrior. When the newly-wed couple returned to Buckingham Palace in the Glass Coach, the police temporarily lost control and a crowd burst through the cordon into the palace forecourt.

The King, who had seemed on the verge of tears during the signing of the register, made no speech at the wedding breakfast, and simply raised his glass to ‘the bride’. He had confided to the archbishop that giving away his daughter was a more moving thing than getting married yourself.

According to Crawfie’s more simplistic view, the wedding breakfast was a ‘merry lunch party’: ‘The tables were decorated with similax [a dark red berried green plant] and white carnations and at each of our places there was a little bunch of white heather, sent down from Balmoral. The famous gold plate and the scarlet-coated footmen gave a fairy-tale atmosphere to it all.’

In fact, the footmen are always left outside the firmly closed Bow Room doors, only appearing when rung for. Inside the sanctuary, the royal family and their guests ate their cold buffet, made the congratulatory toasts and cut the cake – with a sword – which can often lead to a lot of good-natured giggles.

A few days later, when she was back in Athens, Prince Philip’s mother Alice wrote to him: ‘How wonderfully everything went off and I was comforted to see the truly happy expression on your face and to feel your decision was right from every point of view.’ Alice also wrote a detailed twenty-page description of the wedding itself, which she sent on to Philip’s absent sisters.

The princess’s father wrote a letter to his daughter, full of love and pride about how he contemplated his life without her: