Why new Royal Navy coastal submarines would probably be uncrewed

A revived coastal and training submarine capability would more likely take the form of uncrewed underwater vehicles deployed by larger submarines than a new class of conventional diesel boats.

Question

What would a new Royal Navy diesel boat for training and coastal defence look like?

Short answer

It would probably be an uncrewed underwater vehicle rather than a conventional diesel submarine.

Notes

Systems already entering development offer a different answer from reviving a 1990s-style diesel submarine. Early UUVs can support coastal defence and task groups, while future submarines may act as command ships for several distributed undersea vehicles. That structure pushes sensors and weapons outward and enlarges the submarine's effective search and attack perimeter. The same task-group logic also informs discussion of future surface combatants built around uncrewed auxiliaries.