I've been listening to Dan Carlin's Hardcore History for a couple of years now and he is the best of the best. Self described as a part story-teller and part analyst, Dan provides high quality, professional audio podcasts.
If you haven't yet branched into listening to Podcasts, then you are missing out. Living alone most of the time in mission, I spend many peaceful hours painting and building to audio books and podcasts which, unlike video enables me to absorb much entertaining content at the same time as I create without distraction.
Dan is an American with a high degree of humility inasmuch as he has a bachelor's degree but does not label himself an historian. I disagree with this self-assessment but wherever definition you insist on hanging your hat on, Dan is if nothing else a hell of an engaging historical story-teller.
His episodes are often very substantial (over an hour) and often come in several parts. I'd suggest his subject matter serves as a vehicle for discussion and an exploration of ideas. Historical perspective is everything and his curious mind hits his subject matter in similar ways to my own - so I relate to his work.
He is an engaging speaker and I seldom tire or mentally wander off even during his longer deliveries. His product is a professional one with a small team developing the finished product which takes weeks and months to produce.
I used to listen to his podcasts through my iTunes subscription but have recently turned to accessing podcasts through the VLC media player. If you have never done this, there are helpful how-to instructions other thoughtful people on the internet have provided.