Normally, except for the Navy, former officers and retired officers are not permitted to wear uniform, but, as Teetime said, they will both have an official connection to the Household Brigade which will entitle them to wear the uniform on certain occasions. I thought the frock coat was a rather nice, understated touch. Stopped the whole thing looking like some Ruritanian comic opera! The curtain tie back ? is called an aiguilette (sp). All household cavalry officers wear them with full dress. Not sure why Harry didn’t have one.