His uncle Needham Langhorne left behind a vast fortune upon his death in 1673, his favourite property being the manor of Newton Bromswold in Northamptonshire.

[4] Langhorne's father (also named William) was himself active in the East India Company, and had residences in Hitchin and in the parish of St Gabriel Fenchurch in the City of London.

Following his father's death he inherited stock in the East India Company, began to make money and was created a baronet (in the Baronetage of England) in 1668.

In July 1672, St Thome was stormed compelling the Sultan of Golconda to approach the British East India Company (EIC) at Madraspatnam.

They strengthened their fortifications at St Thome and established a new camp at Triplicane thereby posing a direct threat to the British settlement at Madras.

The British held a consultation on 2 February 1674, but before the authorities could come to a conclusion of the proposed course of action, news of the Treaty of Westminster concluded between England and Holland reached Fort St George thereby bringing hostilities to an end.

The French at St Thome surrendered to the Dutch on 16 August 1674 who in turn handed over the city to the authorities of the Sultan of Golconda thereby bringing the hostilities to an end.

Trade of rice and corn were forbidden and Madras was required to present a thousand hundred yards of cloth along with an increased tribute.

He was reprimanded by the directors of the EIC "for firing your guns upon the naming of a church by the papists; we cannot approve thereof, and desire to give as little countenance and encouragement to that religion, as they do to ours; and we would have you discountenance, and discourage all of our nation that any ways incline to that profession.

Major James Puckle who was sent to investigate the charges concluded that Langhorne was receiving an annual sum of 20,000 pagodas from an Indian merchant of Fort St George called Casa Verona (Kasi Veeranna).

[2] Of his fortune, his will which was proved on 8 March 1715, left at least £1600 to be used in a similar manner to Queen Anne's Bounty, providing increased income to the clergy of poorer benefices.

Camden History Review 2016 Vol 40 pp 7–9] It was during the tenure of Sir William Langhorne that the residency of the Agents of Madras, a garden-house called the Guindy Lodge, was constructed.