Joseph Mallord William Turner (1775-1851), John Constable (1776-1837), Thomas Girtin (1775-1802) and John Sell Cotman (1782-1842) were part of a pioneering generation who transformed British art and the practice of landscape watercolour. All born within a few years of each other, this remarkable quartet underwent the same professional training and frequented the same sketching clubs, the birthplace of enduring friendships and rivalries. This exhibition will explore the works of these four…