I congratulate the Guardian on this investigation ( Latin American organised crime ‘may operate in 16 European countries’, 13 October ). It has already prompted a strong call from the former Colombian vice-president Marta Lucía Ramírez for effective international cooperation to counter the transnational criminal threat.

I have followed the “war on drugs” pretty closely since I was the British ambassador to Colombia in the heyday of Pablo Escobar, but I was still shocked to learn of the scale of the Latin American criminal presence in Europe, including supposedly political insurgents such as the Colombian ELN and various Farc dissident factions. The fivefold increase in the cocaine trade in the last decade has boosted organised crime on both sides of the Atlantic. It underlines dramatically the failure of the “war on drugs”.

In 2001 you published an opinion piece by me saying that this war was unwinnable and that state supervision of legalised drugs would be preferable.…