Percival was to use the opportunity to make a detailed study of the Spanish defences .
In October 1739 , Vernon sent First Lieutenant Percival to deliver a letter to Blas de Lezo and Don Pedro Hidalgo , governor of Cartagena .
First Lieutenant was to use the opportunity to make a detailed study of the Spanish defences .
In October 1739 , Vernon sent First Lieutenant Percival to deliver a letter to Blas de Lezo and Don Pedro Hidalgo , governor of Cartagena .