Red Dead Redemption 2: Horseman Challenge 9 when Blackwater is locked (and escaping)

Tips for doing this as Arthur: 1. Health tonics for you and your horse - take them after every 5 seconds or so when Pinkertons spawn 2. Horses love affection and comforting them gives them more stamina 3. Take suitable horse for you. I finally managed to do it while riding white Arabian 4. Groom and feed your horse before the challenge 5. Feed yourself Minty Big Game meat (yields a Gold Health Core) 6. Ride through Van Horn when starting the challenge so the game counts your start