Princess Margaret named and launched M.T. British Mariner on 16 September 1948. Contemporary news reports record the tribute that the Princess paid to the seamen of the Merchant Navy for their service during the Second World War and the continuing danger that they endured in transporting cargo to and from the ports of Great Britain. The Times report featured a picture of the young princess shaking hands with an apprentice at the Harland and Wolff shipyard, where the vessel has been constructed.
The 490 foot, 12,000 ton oil tanker British Mariner, built in the Belfast yard of Harland and Woolf, was launched by Princess Margaret a year after she had launched the Edinburgh Castle, one of her earliest official duties after coming of age.