Thanks Viv she was indeed a fine yacht which was in effect the Britannia of its day. I do have some really good postcards of her somewhere but I just cant put my hand on them at the moment which is my usual problem! I did find this one however which shows a small picture of her at the top of a postcard showing her being used to carry King George V to inspect the fleet at a pre-war Naval Review - a role she was used for many times...
Here's another picture I found ... not very big though !! The RMS Persia - she was torpedoed in December 1915 by the U-38 with the loss of 325 lives