When I was in high school during early 1960s, a gentleman working in Delhi in an important position visited our village for a week or so. He was educated and well-informed and often talked about important issues and happenings in Delhi. He had a very nice way to make complex things appear simple which even a lay person could understand easily. Once he gave me a long lecture on the devaluation of Indian rupee against the US dollar (which had occurred sometime earlier) and the type of impact it would have on ordinary Indian citizen in the long run. On another occasion, he talked about the office-cum-residence for Indian prime minister in New Delhi and the reason for having number 10 in its address (10 Jan Path).
It seems India, after gaining independence from Britain, had chosen to have the same type of parliamentary democratic system as Britain and adopted a constitution which was based mostly on the British constitution. Furthermore, realizing perhaps that the position of prime minister was most significant under the new system and might require him to be available to take care of things and make official decisions anytime, the Indian planners decided to have a joint office-residence complex for their prime minister at Jan Path (a road in New Delhi housing government buildings and offices). This basically was similar to the joint office-cum-residence for British prime minister at 10 Downing St. in London. To further emphasize Indian prime minister’s office-residence complex and enhance its public appeal, the planning officials decided to include the number 10 in its address (10 Jan Path, New Delhi), using the same number as in the address for British P.M.’s office-residence in London (10 Downing St.).
Thus the choice to have and name the office-cum-residence for prime minister of India in New Delhi at 10 Jan Path, in the same way as that for British P.M. at 10 Downing St. in London, was historic and deliberate, reflecting the close similarities in two government systems (Indian and British).