You'll be given an eyesight check before you set off. Make sure you bring your glasses if you need them.
Your examiner may come across as "business-like", so don't be surprised or intimidated by this. He's done this hundreds of times and he's not your mate. He's there to examine you demonstrating Advanced Riding skills.
The examiner's a human being and knows you're nervous. He'll give you 5-10 minutes to settle down, so don't get freaked out if you make a few, early mistakes (so long as they're not bloopers).
If you make a mistake, don't obsess about it - and keep going! Don't let one mistake ruin an otherwise great ride. The examiner will cut you some slack and it may only be a discussion point after the test.
LAM Observers coach you to be above test standard before we recommend you sit your test. Trust in the SYSTEM and you'll do great!