The history of the Williamson Magor Group dates back to 1866. In that year, Captain J H Williamson, who was already involved in the management of tea estates in Assam, met R B Magor, an assistant with the Great Eastern Hotel in Calcutta. Their subsequent meetings and association led to the signing of the First Partnership Deed of the company in 1869. This was valid for a period of two years.

The agreement was renewed in 1871 and by 1875, its term was increased to five year periods. The company had its first office premises at 7 China Bazar Street. J H Williamson died in 1898. George Williamson, who had already withdrawn his capital from the business in 1879, died in 1903. In 1904, the Partnership Deed was renewed with R B Magor and J H Williamson's brother - in - law, Robert Lyell, enjoying an equal share. Williamson Magor & Co. worked closely with its  London partnership, George Williamson & Co., the firm which a few years earlier had been started by James Williamson's brother, George.

The fortunes of the Williamson Magor Group grew along with the boom in the Indian tea industry. By the turn of the century, the company was handling the affairs of 44 tea estates. The Group also became involved in other businesses, including coal. Although the Indian tea industry continued to prosper during the First World War, there was an immediate post - war slump around 1920. The situation became worse with the Wall Street crash of 1929 and the ensuing depression. The production levels of tea far outstripped consumption. George Williamson, the London end of the partnership and Williamson Magor, the Indian end of the partnership, consolidated their position in the tea industry through the twenties and the thirties.

R B Magor died in 1933. His grandson, Richard Magor introduced B M Khaitan to the Group. Initially, Briju Khaitan supplied tea chests and fertilisers to the company and had become a friend of Pat Williamson, a grandson of J H Williamson. Williamson Magor & Co. was converted into a Limited Company in 1954. In 1961, a crisis loomed over the company when B Bajoria, an investor, acquired nearly 25% stake in the Bishnauth Tea Company, the flagship in the Williamson Magor Tea Estates. The Khaitan family provided the money to buy out Bajoria's stake. B M Khaitan was invited to join the board of the company and later, in the face of stiff resistance, went on to become Managing Director of the Group.

The Guthrie family was the majority shareholder in the McLeod Russel Group. In 1987, they decided to sell their tea plantations in India. B M Khaitan negotiated with them and bought out the estates. This meant the Williamson Group became the largest private tea producer in the world. George Williamson went on to acquire and manage tea estates in East Africa. This effort was pioneered by Richard Magor. In April 2001, George Williamson & Company, Kolkata and Williamson Magor & Company, Kolkata mutually decided to separate and work independently. As a result, George Williamson & Company, London ceased to be the overseas partners and selling agents for Williamson Magor & Company, who forged their own links and have now developed a competent overseas sales network.

The offices of the Williamson Magor Group were shifted from 7 China Bazar Street to 4 Mangoe Lane in 1894. Originally known as Hampton Court, the premises was redeveloped through the mid 1960s.

Mangoe Lane tells its own story. It was lined with mango trees on both sides and presumably took its name from these, though why the 'e', which normally appears only in the plural from 'mangoes', should have been tagged on is not known.

The foundation stone of the splendid new building was laid on the 24th January, 1966 by Mrs. O. J. Roy.

Rising nine floors from street level, with an attractive penthouse on top of the ninth storey, the building, with its somewhat severe lines, is in keeping with modern trends of architecture.

One of the most important features of the eighth floor is the very well-equipped tea tasting room, which is situated on the north side or front of the building in order to provide optimum working conditions for the "spitting" staff.

The ten storey block - which stands to the present day - was officially opened in 1968. This asset proved to be a valuable investment as a number of floors were let out.