Creative Assembly explains Total War Saga: Thrones of Britannia's place within the wider series

Thrones of Britannia makes significant changes to the Total War formula, said Tom in his preview of Creative Assembly's latest historical offering a couple of weeks back. Focused on the Viking invasion of Britian, Thrones marks the first of the wider series' Saga offshoots. 

With this in mind, what changes can players expect from a design standpoint? Here's CA's Jack Lusted and Al Bickham with everything you need to know: