Built by Harland and Wolff of Belfast, the R.M.S Royal Mail Ship Edinburgh Castle was launched by H.R.H. The Princess Margaret on 16th October 1947. The R.M.S. Edinburgh Castle was the third Union Castle vessel, employed for the South African route, to bear this name. The first R.M.S. Edinburgh Castle was one of the earliest steamships ordered for the South African service and the second was launched from Harland and Wolff's in 1910. The launch of the third Edinburgh Castle by H.R.H. The Princess Margaret was the Princess' first important solo engagement, an occasion marked by the presentation of this gem-set spray of Scottish heather.

Thanking the builders and owners for their gift, H.R.H. The Princess Margaret replied "To christen this ship Edinburgh Castle gives me great pleasure, for it will ever be linked in my mind with that lovely city for which my affection has grown with each visit. I am also particularly pleased to think that this fine ship will eventually sail between the British Isles and South Africa. It was to South Africa that I made my first voyage earlier this year, and with many happy memories of that great country I am glad to launch a ship designed to increase the traffic and strengthen the bonds between the Union and the Mother Country"