He became High Sheriff of Yorkshire in 1718–19, during the reign of King George I of Great Britain, was briefly an MP for Northallerton, calling himself a Whig, and a businessman.
It was a family-managed enterprise, concentrating on sugar production and exports, transportation of goods to supply the colony, and slavery.
Slaves were imported from west Africa, put to work on the plantations, and were objects of lucrative financial trading by the business leaders.
;[3][4] In 1714, Lascelles gained the powerful position of Collector of Customs for Barbados, coinciding with the ascension of the new prime minister Sir Robert Walpole, a Whig.
Lascelles was in charge of collecting duties on Barbados colonial exports (including his own), usually at the rate of 4.5 per cent; this money would then be remitted to the Treasury in London.
[5] Upon George's death in 1729, Henry Lascelles returned to London and became one of its leading businessmen, with offices near the port district.
[10] Extensive business correspondence from the Lascelles and Maxwell firm has survived, and is the basis of modern research work by writer Adam Nicolson.