NEW DELHI: The heads of British domestic intelligence MI5 and the US' Federal Bureau of Investigation on Wendesday made a rare joint address to warn about China's commercial espionage thrust in the West. MI5 director general Ken McCallum and FBI director Chris Wray said the threat from Chinese spies is paramount in both countries and only continues to grow. They were speaking at an event at the MI5 headquarters in London. McCallum said MI5 had sharply expanded its China-focused operations. Chinese intelligence takes a slow and patient approach to developing sources and gaining access to information, and few of those…