As it did everywhere else, the Industrial Revolution stimulated change in Portuguese Africa. It created a demand for tropical raw materials like vegetable oils, cotton, cocoa and rubber, and it also created a need for markets to purchase the expanded quantity of goods issuing from factories. In Portugal's case, most of the factories were located in England, which had had a special relationship with Portugal ever since Philippa, the daughter of England's John of Gaunt, married John of Avis, the founder of the Portuguese second dynasty. Prodded by Napoleon's invasion and English support for the royal family's escape to Brazil, King João and his successors eliminated tariffs, ended trade monopolies and generally opened the way for British merchants to become dominant in the Portuguese empire. At times, that caused friction, such as when both British and Portuguese explorers claimed the Shire Highlands (located in modern Malawi), but for the most part Great Britain supported the Portuguese position in exchange for incorporating Portugal's holdings into the British economic sphere.