just read the earlier bit about being 'very military'.....well it is an embassy :)
he'll get told which Q to wait in outside, then let through about a dozen at a time - it's just to keep the numbers down inside. Once inside, he takes a number, and waits to be called to hand in his paperwork.
then it's a wait (could be 60mins) sitting down in a largeish waiting room, with tea etc available, until he's called for the interview.
this takes place in a room that looks like a post office, with lots of glass screens and other people around you, not a private grilling in an office. It'll be fine