Complex sentence: A note from its driver reveals that he's gone to get some coal and as he may be gone for some time, Mainwaring suggests driving round it, despite Wilson's reservations that they might bog down due to recent heavy rain.
Split into simpler sentences: A note from its driver reveals that he's gone to get some coal. As he may be gone for some time, Mainwaring suggests driving round it, despite Wilson's reservations that they might bog down due to recent heavy rain.