New Delhi, July 10 -- Empires are usually remembered for the wars they fought, the treaties they signed and the territories they conquered. Rarely are they remembered for the paintings that helped forge key alliances.

Yet, in the early decades of the 19th century, as the East India Company scrambled to secure its hold over India against the shadow of an expanding Russian Empire under Nicholas-I, one of the Company's most effective diplomatic allies was not a soldier or a statesman, but a young Englishwoman carrying a sketchbook.

The younger sister of George Eden, the then governor-general of India, Emily Eden accompanied him on an extraordinary journey from Calcutta to Lahore in the early 1830s, when the Company was courting influential...