Alexander Kent 
Darkening Sea 

Soon after taking part in the dramatic capture of Martinique in the Caribbean, Vice-Admiral Sir Richard Bolitho is next despatched to the African coast to gather a flotilla and stop French attacks on British trade routes. But Bolitho must contend with more than Britains old enemyhe must also face the hatred of his flag captain and betrayal by a man he once counted on as his friend.