Beginning in the Middle Ages, England imported tons of tea from China. What could they export? China was draining the British Empire of silver and gold, but did not want their natural resources -until the British began selling them opium produced in India. The flow of gold and silver began to reverse, until 12 million Chinese were addicted to opium. The Chinese government banned the drug in 1729 and again in 1799, but the British found it too profitable to stop the trade. In 1839 a serious crackdown began, when British factories and ports in South China were closed, and 20,000 chests of opium were confiscated.
Under the direction of Foreign Secretary Lord Palmerston AKA Henry John Temple, British forces — 16 warships, including the iron-hulled Nemesis armed with Congreve rocket launchers, and more than two dozen transport ships with 4,000 troops — sailed to China and blockaded the Pearl River, near Humen, just south of Canton. They demanded reparations of £2 million to cover the loss of the confiscated opium chests. When the Chinese refused, the British attacked. In November 1839, the British sank a number of Chinese ships near Canton and over the next 2 ½ years attacked the coast and fought on land with deadly efficiency, killing an estimated 25,000 Chinese with a loss of less than 70 British troops.
The results of the British incursion would lead to concessions, a lasting distrust between the East and the West, and eventually to the Second Opium War. Read more about the Opium Wars at Modern Farmer. Yes, it has some information about opium farming. -via the Presurfer
Tea may have been used in China during that period, however it was unknown in Europe until Portuguese traders started bringing it back home in the late 1500s. Catherine of Braganza, wife of King Charles II of England, introduced tea to the British around 1660. It was extremely expensive and not widely consumed in Britain until the 18th century.
http://www.smithsonianmag.com/history/the-great-british-tea-heist-9866709/
There's a surprise in the article that resonates with today's stories of Chinese adulterated food products.