I think that female naval officers do not carry swords as a rule, having seen them at their passing out parades, but there could be separate rules for such unusual occasions as we have seen in the last few days. The RAF is, of course the most junior of the services and as such would not have long standing protocols on such things as swords.
I wondered if the Princes Royal's choice of trousers was made in order to go with more comfortable footwear, or maybe a more waterproof option. The royal family certainly had a long day on their feet,
Anne the Pleater
I presume to dictate to no man what he shall eat or drink or wherewithal he shall be clothed."
-- The Hon. Stuart Ruaidri Erskine, The Kilt & How to Wear It, 1901.