Mayor of London Boris Johnson's request for water cannon to be rolled out on the streets of the capital is to be challenged in the courts.

The Police Action Centre (Pac) confirmed yesterday that it had been instructed to pursue judicial review proceedings against the decision by the Mayor's office for policing and crime (Mopac) to push ahead with the controversial plans.

Pac legal director Sophie Khan said: "Mopac had a statutory duty to carry out a public engagement process and to consider Londoners' views before taking any final decision.