You can have a viva for any degree,
For Bachelors it's usually if you're close between two grades so they give you a little interview to see if you're on the clever side or retard side.
(Bazongaloid, Thu 2 Sep 2010, 10:42, 2 replies, latest was 16 years ago)

A friend of mine had one at Bachelors level
to secure her 2.1

Most of the people who have undergone vivas that I know of though did it for their doctorate
( Amberl was stripey and dominated Europe, Thu 2 Sep 2010, 10:43, Reply)

He's got his doctorate though, could it be for his fellowship?

(PsychoChomp, Thu 2 Sep 2010, 10:45, Reply)

possible
but it could be he's just late in being called upon to defend his doctorate. It generally requires new work
( Amberl was stripey and dominated Europe, Thu 2 Sep 2010, 10:52, Reply)

little interview to see if you're on the clever side or retard side cup of soup.

Sorry, I've not had enough sleep.
( Monty Boyce, My cheese game is strong, Thu 2 Sep 2010, 10:44, Reply)