Guardian: A police force whose undercover officers were secretly recorded attempting to recruit a spy from an environmental protest group today admitted spending more than £750,000 of public money on informants over four years. Strathclyde police officers were last month recorded offering cash payments in return for information from Tilly Gifford, a 24-year-old activist with Plane Stupid, a group opposed to airport expansion. During almost three hours of audio tapes handed to the …