I remember walking across the Thames after that party at 7:30 AM and thinking "how can this be prohibited?"
Because it was decided back in the early days of the 20th century that it was politically advantageous to make the sovereign right of altering ones consciousness through the use of entheogenic chemicals illegal. The US set the standard and the rest of the world followed suit. Modern drug laws directly descend from this decision. The DEA's refusal to even allow the phrase 'medical cannabis' in the court of law comes directly from this political motivation.
Death to Tyrants.