'Performed', exactly. Actress playing a role.
Which she does really well. As the only surviving Head of State in the world today who served in WWII, and whose husband served in the Royal Navy during the conflict, she really does have a special bond and affinity with the British Armed Forces. It's amazing to think that she's taken part in every Remembrance Sunday commemorations at the Cenotaph since 1946.
A great woman. God Save the Queen.
Why on Sunday?
I think you'll find it was Remembrance Sunday on Sunday, when the annual commemorations and wreath laying take place at the Cenotaph.