Question: In what year did the Britain Burma Society founded under the distinguished patronage of  Earl Mountbatten of Burma, Sir Hubert Rance whose formal prefix Sir was strictly governed by law and custom as an honorific address?

Context paragraphs:
Hubert Rance: Major General Sir Hubert Elvin Rance (1898–1974) was the last Governor of British Burma between 1946 and 1948, during the transition from Japanese to British colonial administration.  Later he became Governor of Trinidad and Tobago.

Countess Mountbatten of Burma: Countess Mountbatten of Burma is a peerage in the United Kingdom encompassing certain of the wives and daughters of the Earl Mountbatten of Burma.  The family seat for the position is at Newhouse Manor, near Ashford, Kent.

Mountbatten Medal: The IET Mountbatten Medal is awarded annually for an outstanding contribution, or contributions over a period, to the promotion of electronics or information technology and their application.  The Medal was established by the National Electronics Council in 1992 and named after Louis Mountbatten, The Earl Mountbatten of Burma, Admiral of the Fleet and Governor-General of India.  Since 2011, the medal has been awarded as one of the IET Achievement Medals.

Statue of the Earl Mountbatten, London: The statue of the Earl Mountbatten is an outdoor bronze statue of Admiral of the Fleet Louis Mountbatten, 1st Earl Mountbatten of Burma, located on Mountbatten Green, off Horse Guards Road, Whitehall, London, England.  The sculptor was Franta Belsky and the work was unveiled in 1983.

Britain–Burma Society: The Britain Burma Society (BBS) is a society founded in 1957 under the distinguished patronage of Earl Mountbatten of Burma, Sir Hubert Rance (formerly Governor of Burma), Miss Dorothy Woodman, the Rt.  Hon. Malcolm MacDonald, the Rt.  Hon. Arthur Bottomley and others.

Marjorie Pratt, Countess of Brecknock: Marjorie Minna Jenkins Pratt, Countess of Brecknock DBE, JP (died 24 August 1989), was a British peeress.  She was the daughter of Colonel Atherton Edward Jenkins and his wife, Anna Isabella (née Schoenbrunn), the niece of Sir Ernest Cassel.  She was a cousin (and life-long close friend) of Edwina Ashley, who married Lord Louis Mountbatten, 1st Earl Mountbatten of Burma.

Edwina Mountbatten, Countess Mountbatten of Burma: Edwina Cynthia Annette Mountbatten, Countess Mountbatten of Burma, ("née" Ashley; 28 November 1901 – 21 February 1960) was an English heiress, socialite, relief worker and the last Vicereine of India as wife of Louis Mountbatten, 1st Earl Mountbatten of Burma.

Earl Mountbatten of Burma: Earl Mountbatten of Burma is a title in the Peerage of the United Kingdom.  It was created in 1947 for Rear Admiral Louis Mountbatten, 1st Viscount Mountbatten of Burma, the last Viceroy of India.  The letters patent creating the title specified the following special remainder:

Sir: Sir is an honorific address used in a number of situations in many anglophone cultures.  The term can be used as a formal prefix, especially in the Commonwealth, for males who have been given certain honours or titles (such as knights and baronets), where usage is strictly governed by law and custom.

Mountbatten Institute: The Mountbatten Institute (formerly known as the Mountbatten Internship Programme) is an organization based in New York and London dedicated to fostering work experience and cultural exchange by placing international graduate students abroad to earn postgraduate certificates and degrees.  Named in honour of Louis Mountbatten, 1st Earl Mountbatten of Burma and benefacted by his eldest daughter Patricia, 2nd Countess Mountbatten, the organization was founded in 1984.

Supporting paragraphs: Britain–Burma Society Sir
Answer: 1957