Surface-to-air missile systems have been deployed at Donald Trump's Mar-a-Lago resort as the Secret Service warns of a "heightened threat environment". Two Avenger air defence systems have been placed on a floating barge near Mr Trump's Florida residence, according to photos published by the Palm Beach Daily News. "The US Secret Service is operating in a heightened threat environment, and we continuously adapt our protective operations to incorporate cutting-edge tools, technology, and methods to safeguard our protectees," a US Secret Service spokesman told The Telegraph.