If you look up "interception" in most dictionaries you’ll find that it happens before an action has completed: in sport a pass can no longer be “intercepted” once it reaches a teammate. In a legal dictionary, however, that turns out not to be true. According to section 2(2) of the Regulation of Investigatory Powers Act 2000 (RIPA) interception can take place at any time when a message is "in transmission", which is explained by section 2(7):
