Judge Peter Openshaw broke into the questioning of a witness about a Web forum used by alleged Islamist radicals.
"The trouble is I don't understand the language. I don't really understand what a Web site is," he told a London court during the trial of three men charged under anti-terrorism laws.
Prosecutor Mark Ellison briefly set aside his questioning to explain the terms "Web site" and "forum." An exchange followed in which the 59-year-old judge acknowledged: "I haven't quite grasped the concepts."