British security group G4S on Monday said it had agreed to buy Danish facilities company ISS for £5.2 billion ($8.2 billion, 5.9 billion euros), creating the world\'s largest security and facilities group. \"G4S plc, the international security solutions group, today announces the acquisition of ISS A/S for an enterprise value of approximately £5.2 billion,\" a statement said. \"We are excited to announce the acquisition of ISS to create the world\'s largest integrated security and facilities services group,\" G4S chief executive Nick Buckles added. G4S shared plunged on the London Stock Exchange, sinking 39.30 pence or 13.92 percent to 243 pence.