A former Metropolitan Police commissioner has called for an "urgent review" of Britain's cannabis laws.
Bernard Hogan-Howe said the government should look to reexamine the debate around cannabis in light of recent changes in legalisation in north America.
Canada legalised recreational cannabis in June this year, while the drug is legal in nine states in America.
His comments come after four decades of an unsuccessful United Nations coordinated war on drugs which has actually seen a rise in the number of deaths related to drugs.
As a former senior police officer, Lord Hogan-Howe led that fight on the streets of Britain and has always supported tough legalisation banning cannabis. But now he says the time has come to reconsider the UK's stance on drugs.
He said: "We already know from the evidence around the world that where people use it for medicinal purposes, it slides into recreational.
"Surely it's better that we get ready for that potential change.
"I've not seen clear evidence to say change the law now. But I have seen clear evidence to say let's review it, but in a time-limited way, not a kicking into the long grass way.
"I think we need to get on with it, now the Government has made it easier to get medical cannabis on prescription.
"We're lucky - we're not the pioneers and we can learn from others' mistakes. The evidence is out there and it shouldn't be ignored."
Doctors will be able to prescribe cannabis products to patients in England, Wales and Scotland from November 1.
A spokesman for the Home Office said the government has "no plans to decriminalise recreational cannabis".