Lieutenant Ayers was a Provost (something of an early form of Military Police), one of three "mounted on black horses and standing like highwaymen waiting for a plump coach" in a small deserted Portuguese village. Their equipment was reported as new, and their faces burned red, indicating that they had newly arrived on the Peninsular.
After some verbal sparring with Captain Sharpe, Lieutenant Ayes and the two other Provosts went to examine Sharpe's men, and he caught Private Batten red-handed, with a stolen chicken. Ayers determined that Private Batten must be hung, and only armed intervention by Sharpe and Harper stopped it happening (Sharpe's Gold : Chapter 1).
Subsequently, Sharpe was forced to apologize to an embarrassed Lieutenant Ayers, in the company of the Provost Marshal and Colonel Williams. Sharpe's smart apology caused Ayers to agree to his own regret over the incident, to the confusion of Colonel Williams (Sharpe's Gold : Chapter 3).