Is it time to make cannabis legal in the UK? Today, the Evening Standard launches a major investigation to find the right answer.

A decade ago, the question seemed eccentric. Today it is mainstream. In the past couple of years, large parts of the western world have passed laws that legalise the drug.

Tens of millions of people living in Canada, California and Colorado have seen cannabis go from being bought from drug dealers on street corners to being sold largely as a commodity in shops and marketed on billboards. New York and Chicago are following suit.

In Europe, things are moving fast too. Spain is allowing its private use, while Portugal is decriminalising it.

Here in Britain, when the Government tried last year to stop children with epilepsy using cannabis oil to ease their suffering, there was a public outcry.

Our sensible Home Secretary, Sajid Javid, overruled the current Prime Minister and since November use of the drug for medicinal means has been permitted here.

Certainly our police have backed off enforcement of the current laws, whatever is said publicly. Anyone who walks around this city can smell that — and it’s reflected in the fact that prosecutions for possession are down by over a third in just five years.

But is the UK ready to make the leap and make cannabis legal?

Our exclusive poll today says 63 per cent of Londoners and 47 per cent of people across the UK are in favour — with less than a third against.

It is a huge shift in public opinion that has happened with our political classes barely noticing.

That doesn’t mean they are right. As we have argued on other issues, we live in a representative democracy rather than through government by opinion poll.

Parliament must weigh up the pros and cons carefully. That is what the reporting by our award-winning investigations editor David Cohen will seek to do.

Would legalising cannabis add significantly to our health problems as a nation? Some say yes, and point to the links between the drug and psychosis. Others say the harm is there already — make it legal and we can treat the problem.

Would legalisation lead to an increase in disorder? Some agree — we don’t want people high on our streets and roads. Others say no — if you remove the criminality around a drug that is used regularly by millions of people you remove much of the crime.

The interview today with the special police constable who spoke from experience on TV’s Question Time, and then was pushed to resign, is telling.

What would happen to revenues if the drug was legal? Huge new companies have sprung up in the US, and states there will collect billions of dollars in new taxes to spend on public services. We could do the same here. But what happens to those profiting from the illegal drug trade today, some of whom are themselves very vulnerable?

These are just some of the searching questions the Evening Standard will address over the coming month.

We’ve seen before how quickly social mores can shift, and catch those who govern us unaware. What society once regarded as obviously illegal —from abortion to attempted suicide, and from homosexuality to gay marriage — can become near universally accepted in a short period of time.

Whether we resist it or embrace it, one thing is clear when it comes to the debate about legalising cannabis: the times they are a-changin’.

London’s new museum

There are around 200 museums in London but only one of them is the Museum of London — which has told the capital’s story from pre-history to the present day at its site on London Wall in the City since the Seventies.

Now it is making plans for a move to Smithfield, setting out details today of what will be the most extraordinary urban museum in the world — reaching down to the Tube lines and the buried River Fleet, which run deep beneath the site.

It’s a hugely ambitious project: converting old market buildings will be expensive.

Raising funds won’t be easy but these plans deserve to succeed.

We can’t wait to see it open.