“Don’t forget that when she turns up somewhere, the crowds are two, three, four, 10, 15 deep, and someone wants to be able to say they saw a bit of the Queen’s hat as she went past.”

In today’s portrait, the Queen is also wearing her usual choice of jewellery, which includes three strands of pearls around her neck and a brooch pinned to her dress.

The Queen chose to pay tribute to her late mother, Elizabeth, by wearing the two diamond clips.

Given to the monarch by her mother on her 21st birthday in April 1944, both clips are in the shape of an ivy leaf.