As much as one-tenth of Britain’s national revenue derived from the trade at Canton

The [East India] Company’s income from the China trade was completely swamping its revenues from India: in the first decade of the 1800s, the imports from Canton provided two-thirds of the entire sales income of the East India Company in London. By the latter part of that decade the China portion of its trade was bringing in record profits while the India trade operated in some years at a net loss. The effect was, first, to create a huge increase in the government’s tax revenue from the China trade—to the point that by some estimates as much as one-tenth of Britain’s national revenue derived from the trade at Canton. By corollary, the growing reliance of the British government on its tax revenues from the Company’s tea also meant that the stability of affairs in Canton became a matter of serious national interest. Any interruption to the China trade could interfere with Britain’s ability to finance its war. 

S. R. Platt, Imperial Twilight (2018), 88-89