As
EODFelix has rightly said they haven't amalgamated again. I was looking them up in Lt Col Robin Hodges excellent book
British Army Badges and that scarlet uniform worn by Captain Phillips for the wedding doesnt seem to figure, officers are portrayed wearing dark blue (or black?) No 1 Dress, so I think it must have been a one-off. Good excuse for Wills to go for it.
Talking of tradition, is the brides father paying for the do ?
They may have a better do if he does. A mate of mine was in Royal Protection and he told me the Windsors are notably stingy when it comes to shelling out their own money. Mind you I guess we'll be paying
