At a basic level, a Product Owner seeks to deliver maximum value out of their product. Piers likes to think of an Agile Product Owner as the 'CEO of the product' who is customer-centric and works collaboratively with engineers to provide solutions to customers' problem statements and their continual feedback.
In his conversation with Andrew, he talks about the segmentation of functions within financial institutions being a prime obstacle to the empowerment of Product Owners to create Agile products through an Agile process, as well as the amalgamation of multiple roles with overlapping product responsibilities.