The third volume of these letters begins with Macaulay preparing to sail for what he regarded as his exile in India. It ends in 1841 with the defeat of the Whigs, whose ranks he had rejoined following his return from India and who had raised him to cabinet office. The nearly eight years between these two points are filled by his activity as a legislator in India and by his return to English politics, beginning with his election for Edinburgh in 1839. At the same time he continued to write for the Edinburgh Review, contributing from India the ambitious essays on Mackintosh and on Bacon, and, after his return, the essays on Clive and on Hastings that embody his reflections on the imperial venture in India.

These years were marked, in Macaulay's private life, by two devastating events. His sister Margaret died shortly after he reached India, though the slowness of communication from England meant that Macaulay did not learn of her death until months after his arrival. When, at the beginning of 1835, Macaulay at last received the news of Margaret's death, he was already in desperate emotional straits in consequence of the marriage of his sister Hannah, who had accompanied him to India and who had married a young civil servant within a few months of their arrival. He thus lost both sisters at very nearly the same time.

The marriage and the death were both traumatic events. They cost him bitter suffering, and they left permanent marks on him.