A spokesman for the Met Police said: "Police were called at 12:09hrs on Saturday, 22 February following reports of a large crowd gathering in Soho in relation to an apparent marketing stunt that had been advertised online.
One boy, wearing a part of a police uniform, including a Met jacket and police cap, was spotted rummaging around in the vehicle, before jumping back on top of the roof.
As the Met Police arrived at the scene, blaring sirens, many of the teens fled and two boys, both under 16, were arrested.
"Officers have since arrested two boys under the age of 16, on suspicion of theft from a motor vehicle, criminal damage and affray.
The streetwear brands, Up In Flames and Poser, were giving out clothes from a van in Carnaby Street but thousands of people surrounded the van within minutes.
