A grandmother who was spared jail after making cannabis-laced casseroles for herself and friends was one of the speakers at a pro-cannabis rally.
Patricia Tabram baked biscuits and soups with cannabis
Patricia Tabran, 66, spoke at the Cannabis Education March and Rally in Trafalgar Square, central London.
Ms Tabran, from Northumberland, admitted in April to possession with intent to supply and was given a suspended six-month prison sentence.
The march began in Russell Square, central London, at 1300 BST on Sunday.
The annual event usually takes place in south London.
But Lambeth Council would not permit the seventh Cannabis March and Festival in Brockwell Park, Brixton, because of drug dealers at previous events.
However, the Greater London Authority has allowed it to go ahead.
Organisers of the Brixton festival said they were aware of drug dealers being present but had wanted to work with Lambeth Council and the police to stamp out the problem.
Other speakers at the event included Peter Tatchell from gay rights group Outrage and Roger Warren-Evans, barrister for human rights group Liberty.
The subject of returning cannabis to a Class B drug after it was downgraded to Class C will be discussed at the rally as will health concerns, drug testing and driving under the influence.
Campaigners say they want the drug regulated and say legalisation would not lead to increased use.