Down 54-52, Britt's layup tied the game at 54 with 3:08 remaining. Thornton then scored four straight points -- a layup and two free throws -- to put William & Mary ahead 58-54 with 1:59 left.
Towson managed just two points in the final 2 minutes while William & Mary converted five free throws in the same span to seal the victory.
The Tribe made 12 free throws for the game compared to four for the Tigers.
Marcus Damas scored 13 points and grabbed seven rebounds for the Tigers (10-12, 5-4), who have now lost three straight.
Guard Naz Mitrou-Long, whose 2015-16 season ended in December due to hip problems, has been granted a hardship waiver for the coming season, Iowa State said.
As the Sooners look to life without superstar Buddy Hield and his sidekicks, it's clear their unseasoned players will need to grow up fast.
The Central Intercollegiate Athletic Association says it won't move its headquarters, its basketball tournament or other conference championships from North Carolina, despite