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William Mackinnon and William Mackenzie (ca.1810-d.1853) were partners as a general merchant near Calcutta
1856 Mackinnon, Mackenzie and Co secured the East India Company's mail contract between Calcutta and Rangoon and founded the company which was registered in Glasgow on 29 September as the Calcutta and Burmah Steam Navigation Co.
1862 Having expanded its trade, the company name was changed to the present title  and six larger ships were ordered. Mackinnon, Mackenzie & Company in Calcutta continued to operate as the managing agents.
1874 The first service to and from the United Kingdom was inaugurated, from London to Aden, Karachi and the Gulf, to take advantage of the opening of the Suez Canal.
1876 A second service to the UK, from London to Calcutta by way of Suez, Colombo and Madras, was established
1881 to 1895 A mail contract with the Queensland Government.
1890 Started a regular service from London to Zanzibar via Aden and Mombasa
1914 Amalgamated with the Peninsular and Oriental Steam Navigation Co
WWI Heavy losses of ships
Post War: A massive replacement programme led to the company becoming the largest single merchant fleet in the world in 1922 with 158 vessels.
1934 Acquired a controlling interest in Asiatic Steam Navigation Co.
1935 Both Asiatic and Mogul Line became part of the P&O Group (Mogul was sold to Indian interests in 1960)
1961 acquired the remaining Asiatic shares.
1971 Major restructuring of the P&O Group into "operating divisions". As a result, the remaining cargo liners and passenger/cargo ships in the Indian Ocean and the Gulf were transferred to P&O General Cargo Division and the educational cruising was operated by the new Passenger Division.