Angel was a Spanish boy, the son of a cooper.
His parents died at the hands of French dragoons, his mother was raped, and when his father tried to save her, he was murdered, and then she was killed as well. He, a 13 year old boy, had witnessed the killings, the destruction of his home, and of his father's shop. That same night, with only a knife in hand, he had killed his first Frenchman and escaped. He buried his parents, and put the knife he had sought revenge with in their grave. Then he went to find the partisans.
He was instead discovered by one of Hogan's Exploring Officers. He was taken to Hogan, who then used the boy as a courier. Too young to be seen as a threat to the French, he moved largely unobserved. He refused a wage, taking only a Baker Rifle and the opportunity to kill the French as his compensation. Three years later, it was Angel who Hogan assigned to be Sharpe's backup in his mission to find La Marquesa.
Angel told Sharpe he would join the Rifles, and proved during Sharpe's Honour, he could handle a rifle as well as any man in Sharpe's company. He followed Sharpe when he was captured by the French, and sought him in the town, waiting for days outside, after the destruction of the powder magazine, to see if Sharpe would escape. He then provided horses for their trek back to British territory. Sharpe told him of the French plot to get the British out of Spain, and than forbade his fighting at Vitoria so that if Sharpe were killed, Angel could still get the news to Hogan.
Note: Angel never appeared in the television movies. His role in Sharpe's Honour was taken by Patrick Harper.