I'm building a site in CakePHP 5; I've made the main part of the site but now I'm building the admin area and getting an error.

I've set up my routes with an admin prefix, like this:

   $routes->prefix('Admin', function (RouteBuilder $routes) {
     $routes->connect('/', ['controller' => 'Pages', 'action' => 'index']);
     $routes->connect('/pages/index', ['controller' => 'Pages', 'action' => 'index']);
     $routes->fallbacks(DashedRoute::class);
   });

I've created PagesController.php in src/Controller/Admin and it has an index function:

class PagesController extends AppController
{

    public function initialize(): void
    {
        parent::initialize();
        $this->loadComponent('Authorization.Authorization');
    }

    public function index($name = null)
    {
        $query = $this->Pages->find();
        $query = $this->Authorization->applyScope($query);
        $pages = $this->paginate($query);

        $this->set(compact('pages'));
    }
}

and I have templates/Admin/Pages/index.php.

When I try to navigate to http://localhost/sites/HMIPS/admin/pages/index I get the error Controller class `Pages` could not be found and a MissingControllerException.

What am I doing wrong?I've built similar sites before, but using CakePHP 4, so I don't know whether there's something new in version 5 that I'm missing. Is there anything else I need to set up to make this work?