Suddenly a plain clothes policeman – a burly guy with a bomber jacket, jeans, trainers – shows me his card. I almost laugh, it seems so ludicrous. “Very sorry, we’ve had a tip off about illegal trading.” Oh shit. Around me all falls silent, the pressing team looks horrified. “We’re… we’re not trading… we’re asking for a donation… we’ve been picking with all the local schools,” I stammer. “It doesn’t say donation,” says the policeman pointedly. I wave a frantic hand at one of the helpers and she quickly grabs a marker pen and modifies the notices. “Suggested donation for a glass of fruit juice…”. The policeman grins and scrabbles in his pocket for a donation.