I love balance, and think I've been unlucky with the guest speakers on my P&O cruises. Not seen Dickie Arbiter on a cruise (though he's frequently on TV), but Jenny Bond was on one of our Cunard cruisers and she was good.
For even more balance, on our last Cunard cruise in (I think) June 2019, the guest speaker was Martin Bashir. Even without the benefit of hindsight, he was absolutely dire, though he was actually doing the lectures as the Beeb's Religious Affairs Correspondent, not their finest HR vetted appointment...