Complex sentence: It wasn't until later that Captain Martin may not have been at fault as the Chief Engineer J.V. Reader had reduced the speed of the vessel as soon as she left port bypassing Captains orders to proceed full speed.
Split into simpler sentences: It wasn't until later that Captain Martin was not to have been at fault. The Chief Engineer J.V. Reader had reduced the speed of the vessel as soon as she left port, bypassing Captains orders to proceed full speed.