Balmoral Tartan at Balmoral. 1

[Downunder Kilt]

Here is a link to a article which shows what the Queens piper was wearing in 2010
http://tour-scotland-photographs.blo...-scotland.html

It is the Balmoral tartan.

Update
I have done a bit more research and the photo in the link above, although put on the web in 2010 appears to be of PM Jim Stout who was the Queens Piper 2003 - 2006. If one does a search of the web, you can find various Queens pipers in a variety of tartans at different events. I would imagine that if the PM was not performing duties for the Queen at Balmoral, then he may wear his regiments tartan or another tartan associated with the Royal Household.