The most expensive home sale in recorded history didn’t happen in Manhattan or Beverly Hills. It happened in a 19th-century Georgian mansion tucked inside the grounds of a London military hospital — and the man who wrote the check is a billionaire most Americans have never heard of. Suneil Setiya, co-founder of the London-based quantitative trading powerhouse Quadrature Capital, has been identified as the buyer of Providence House in Chelsea, according to the Financial Times . The estate is a