So I'm reading A RISING MAN by Abir Mukherjee, set in 1919 Calcutta, and the (British) protagonist is ruminating about the opium dens of Little Chinatown and how the British police there should probably not bother cracking down on them since "we'd fought two wars against [Chinese] Emperors for the right to peddle the damn stuff in their country. And peddle it we did. So much that so that we managed to make addicts out of a quarter of the male population . . . [which] probably made Queen Victoria the greatest drug peddler in history" (63).

What wars is the author referring to? And were they really fought for this reason? And can someone be more specific about what rights were won and how that resulted in the drug trade?

Is this something that the average Brit knows and accepts?

Is this aspect of Queen Victoria's rule commonly represented or is it mitigated or minimized or marginalized somehow?

Any insight would be very appreciated.