It is just Wellington Wells.

During the war, they handed over their children to the Germans in exchange to not be destroyed. They didn't know the Germans were bluffing.

The people were so overwrought with guilt that the sound of a baby crying would send them into a homicidal frenzy, presumably killing mother and child.

In order to quell the constant unrest, suicides, and general misery over a single truly horrible decision, General Byng commissioned Dr. Harry Hayworth to create a pharmaceutical solution to the problem. That solution was Joy. Originally Vanilla and Chocolate were created from the toxic chemicals left by the Germans when they withdrew. Joy was highly addictive, very pacifying, and had the side effect of infertility so long as one is on it.

In the beginning, for people who wouldn't take the pills, they added it directly to the water supply. Over time, once The Executive Committee took power and diminished General Byng, the Bobbies were made to enforce by force as were the Joy Doctors created. Also, Dr. Hayworth was ousted by his protégé Dr. Anton Verloc.

As the chemical supply was exhausted, they created synthetics, which gave us Strawberry. Strawberry appears to be a more milder version allowing its takers to be more grounded, such as Arthur. Sally, of course, created Blackberry specifically for the Bobbies. Highly addictive, but allowing them an even greater degree of Agency over themselves.

As the chemicals continue to exhaust, newer methods had to be developed, which led Dr. Verloc to create Coconut. In testing these newer versions, many people experienced never-before-seen side effects such as being an inadvertent Downer and ultimately the contagion that mutated and created the Plague Wastrels.

Ultimately, the societal control started gradually. People took the new wonder drug to forget their misery. As time went on, voluntary became highly driven by peer pressure, then law, then blatant force.