British India Steam Navigation Company ("BI") was formed in 1856 as the Calcutta and Burmah Steam Navigation Company. The company had been formed out of Mackinnon, Mackenzie & Co, a trading partnership of the Scots William Mackinnon and Robert Mackenzie, to carry mail between Calcutta and Rangoon. It became British India SN Co in 1862. Under the hand of Lord Inchcape, who had become chairman in 1913, the company became part of the P&O group of companies in 1914 through a complex amalgamation, but continued with its own identity and organisation for another nearly 60 years until 1972, when it was entirely absorbed into P&O.