rule 1: there are no rules for the UK viva/defense
rule 0: it is nice the calm the student down at the start
and one way to help is to ask them to do a brief (max 20 mins, preferably 10 mins) outline of the contributions of the research - if they insist on slides, ok.
typically should list 3 main new ideas, methodology(s) and results (and possibly consequences for future research(ers).
rule 2: take a break if the viva looks like taking more than 90mins.
rule 3. unless there's something weird going on, a viva rarely takes less than 60 mins
rule 4: if you hit 5 hours, you are doing something even weirder.
unless (happened to me) the work has led you (the examiners) to come up with a new idea and you are writing a paper about it.
rule 5: make sure reports a(especially written feedback including _detailed_ specification of corrections) are made available the _day_ of the viva, or even right at the end of the defence if you bought them with you.
rule 6: there are usually two examiners, one of whom is from same institute as candidate (though not necessarily same department) and should not be a conflict i.e. wasn't supervisory in any way nor co-authored any papers on the work doing the research. Sometimes the local examiner is there "just" to make sure rules/process is followed fairly, and may not know a lot about the topic. That said, they should still have read the dissertation and written a report and have questions to ask. Sometimes (rare), the local examiner can be a bit bossy, and the external should say that they are there to maintain comparison/quality control so the internal isn't meant to override that aspect of things.
rule 7: there are sometimes extra people (e.g. from faculty, or from some due diligence bit of the institute. If the student is super nervous, they can sometimes request for an advisor or friend to attend, though normally, those people are not allowed to say anything in the viva.
rule 8: as an examiner you should have read the thesis. three times. and written notes on it. and checked everything in maths, analysis, graphs, equations, algorithms, and results. and bibliography. and any legends/tables. and related work.
and written a report and (if there are minor) list corrections - and suggestions for improvement (e.g. to structure) or additional experiments needed (with a justification as to how they will support the argument) if you think its needed.
rule 9: the viva may change your opinion as to the outcome. usually this may be to convince you that corrections could be minor rather than major. very occasionally (rare0 that there's a major problem you had not perceived - sometimes the other examiner might raise this.
rule 10. you should have exchanged reports and recommendations with the other examiner ahead of the viva (worst case, delay starting the defence for 10-15 mins to discuss how to run it given your questions)
rule 11. questions? yes, you should have a list of questions to ask the candidate. not just corrections. question 1 leads to rule 0. other questions are about background, and then about methodology or clarification of results.
rule 12. if the work is inter-disciplinary, take care to respect that you may not know much about the "other" discipline, and the other examiner might do, and that a grade should not be the average of your two views, but the sum.
rule 13. there are no rules.
Rule 14. If in doubt, ask for faculty input/advice.
Rule 15. Outcomes are (usually):
Pass, minor corrections, major corrections, resubmission, fail (sometimes with option for masters)...
Minor corrections are things that take some number of days max and are usually "cosmetic"
Major corrections may involve modest amounts of new work
Resubmission involves perhaps significant additional work, but on the order of max a year
Fail is very very rare. And should involve serious conversation with the
faculty as something went wrong if a student was allowed to(or insisted)
to submit something like that. Indeed, If it is the first examination of
the thesis then the student can’t usually fail - the worst case is a resubmission.
In my experience, pass is about 5% of the time. Minor corrections something like 75% of the time, major corrections 10%, resubmission 5% (in supervising 60 students, I had 1 fail with just a masters) but these stats probably vary by discipline.
Rule 16. In the first 3 (or even 4) outcomes, the student should be congratulated and possibly there will be a post viva celebration, though nothing as fancy as the Scandinavian Karronka (no sword and hat either, sadly).
Rule 17. Before ending, give the student the opportunity to volunteer things they'd like to have been asked about!
Rule 18. Some institutions don't let you tell the student the "result", although obviously if there are corrections, you have to communicate them with the student, and if there are no corrections, then they can infer the result (if they can't, then they don't deserve the phd:-)
Rule 19. It is fairly standard to ask the student to wait somewhere at the end of the actual viva so that you and the internal examiner can discuss the outcome, and possibly finish any point report/ feedback, before inviting the student back in to the defence to tell them the (hopefully good) news...
Rule 20. There is no rule 20, nor are there any other rules.
