He was quickly shut down by Theresa May, who categorically ruled out legalisation or even decriminalisation [1].
I don't understand how politicians can stand up and claim that legalisation would have substantial negatives, when every experiment with legalisation has been a success. It's the same blinkered thinking as the anti-gay marriage politicians claiming that it will cause the breakdown of families, or politicians claiming that universal healthcare in the USA clearly wouldn't work.
Drug prohibition has been a categorical failure in every outcome it was intended to achieve. It has cost governments trillions of dollars and incarcerated millions, funded terrorism and civil wars, and caused the deaths of millions of people from both violence and drug related harm. Plus the harm caused by the demonisation of drugs that have potentially powerful positive effects as part of psychiatric treatment such as LSD and MDMA. All due to some concept that taking "recreational drugs" is a moral failing and hence should be illegal.
At least society in genera has finally come around to realise that drug addiction and drug use are not moral failings (although my parents aren't quite convinced).
Obviously we want to restrict access as much as possible to particular drugs, such as heroin or methamphetamine, which are so harmful and addictive that nobody should be using them, or GHB, where the potential for fatal overdose is so high. But penalising the end user is not the solution. People who want to take drugs will take drugs. I have never met somebody who has decided to not take a drug because it's illegal. Whether it was alcohol when underaged, smoking a joint, injecting heroin, or snorting cocaine. I know plenty of people who don't take drugs as a personal choice or because they get drug tested at work, but never was the law a reason why the abstained. It doesn't restrict supply either. Drugs are easy to find and readily available practically everywhere in the world, all that prohibition does is push up the price, fund criminals, and increase harm due to poor quality control and cut drugs.