Dartmouth House is a large and luxurious Georgian house in Mayfair, central London, England. It now acts at the headquarters for the English-Speaking Union (ESU), an educational charity. It is located at 37 Charles Street, southwest off Berkeley Square.Over 40,000 people use the building each year. The original building was constructed in the mid 18th-century and what today comprises Dartmouth House was two separate residences, numbers 37 and 38 Charles Street. The first owner of number 37 was Henry Herbert, 2nd Earl of Carnarvon from 1757–1776.