At the age of eight he was living with his uncle Alexander in Deptford, Kent. (Why?)
Alexander was purser of HMS Hannibal. This was a two decker 74 gun navy warship built in 1810. The week before writing his will the Hannibal was involved in action against the French. On March 27th 1814 the Hannibal chased and overwhelmed the French 40 gun frigate Sultane off Cherbourg. After a "desperate engagement of 2¼ hours in which the enemy had 40 men killed and 71 injured" the Sultane was taken back to Portsmouth to be re-fitted as a British warship. (For a brilliant portrayal of a sea chase and capture see the film "Master and Commander" 2004)   Warships often patrolled in squadrons led by the flagship, usually the largest ship. Hannibal's senior officer, Captain Seymour, controlled the squadron. The purser, who wore a bicorn hat, fore and aft and white trousers, was, like the master, a warrant officer, i.e. not drawn from gentry. His pay would have been around £47 per year, half that of the Master, but four times that of an ordinary seaman. His rank was roughly equivalent to a Lieutenant though he probably had a better cabin. A "purser" was not really a naval job. His training would have been on land. He was in charge of all provisions and took a 5-12½% cut on all transactions. Corruption was a temptation that went the the job i.e. giving short rations of tobacco and pocketing the shortfall. The purser was often the most hated man on the ship. A warrant officer might stay with one ship for his entire career, un-like regular officers who tended to move from ship to ship.
The Times obituary described Alexander as "respected by all who knew him and an ornament to his profession"

    
                                                                                          
Will available on line ref:11/1603
His Majesty’s Flagship Hannibal at sea 2^nd April 1814 (where no stamp is to be had).
I, Alexander Usborne, Purser of his majesty’s ship Hannibal number on the ships books 151 being in bodily health and sound and disposing mind and memory and considering the perils and dangers of the seas, do make, publish and declare this my last will and testament: 
First I commend my soul to God and my body to the earth or sea as it shall please God to order. As for and concerning all my worldly estate I give, bequeath and dispose thereof: All prize money …….or property whatsoever that may become due after my death and all wages, sum or sums of ………lands ……goods and chattels and estate whatsoever shall be any ways due, owing or belonging unto me at the time of my decease. I do give the same unto my beloved wife Margaret Usborne and at her death to be equally distributed to our children lawfully born or begotten and at the age of twenty one years, four hundred pounds to be given to each out of the 520 stocks of the three percent consols. 
Alex Usborne, signed sealed, published and declared in the presence of us at sea, Eclan Derouche, Lt., Hannibal; William Amey, Master, Hannibal