Back home, Cox's house on Albemarle Street (opposite the present-day Ritz Hotel) was known for its parties. In addition, he was a patron of the arts, being acquainted with David Garrick and other notable actors of the time, and was a founding financial investor in the rebuilding of the Theatre Royal in Drury Lane. He was also a generous benefactor to St George's Hospital on Hyde Park Corner (now the Lanesborough Hotel). The records of the family estate at Quarley show that Cox spent over £3,000 per annum running it, much of it lavished on his wife.