In their first joint appearance, the heads of the FBI and MI5 appeared together in London to warn of security concerns posed by China and said the government in Beijing was the biggest long-term threat to the U.S. and its allies. #MI5 #FBI #China #USA #UintedKingdom #News #Reuters Subscribe: http://smarturl.it/reuterssubscribe Reuters brings you the latest business, finance and breaking news video from around the globe. Our reputation for accuracy and impartiality is unparalleled. Get the latest news on: http://reuters.com/ Follow Reuters on Facebook: https://www.facebook.com/Reuters Follow Reuters on Twitter: https://twitter.com/Reuters Follow Reuters on Instagram: https://www.instagram.com/reuters/?hl=en