The story is deeper than that. The Chinese liked to get paid in silver for their products (tea, porcelain, silk). Unfortunately silver is what the British money was made of (the pound sterling meant a pound of sterling silver = 92.5% pure). So it was creating a currency shortage. Britain thus wanted a product to balance trade and stop the silver outflow. Opium was that product.
The Chinese didn't want their people hooked on Opium, so they made it illegal. British trading companies that supplied the opium (it was grown in India at the time) formed a cartel to bring it in illegally, thus becoming the first drug cartel. When their people got arrested and goods seized, the British government forced China to submit in what is known as the Opium Wars. They acquired Hong Kong in the process. Later, the now legalized trading companies needed financing for the ships to deliver the expanded opium trade. So they founded the Hongkong and Shanghai Banking Company. Now known as HSBC, one of the largest banks in the world, it is no stranger to laundering money for cartels, because it was*founded* by drug cartel members. To this day they print paper bank notes (currency) for Hong Kong. This makes money laundering really easy, because they can give you a suitcase of brand new money, with no traceable history.