Rank structre of two public setors
The rank structure of two contrasting uniformed PES sertors
The first lieutenant in the Royal Navy and other Commonwealth navies, is a post or appointment, rather than a rank. Historically the lieutenants in a ship were ranked in accordance with seniority, with the most senior being termed the "first lieutenant" and acting as the second-in-command. Although lieutenants are no longer numbered by seniority, the post of "first lieutenant" remains. In minor war vessels, destroyers and frigates the first lieutenant (either a lieutenant or lieutenant-commander) is second in command, executive officer (XO) and head of the executive branch; in larger ships where a commander of the warfare specialisation is appointed as the executive officer, a first lieutenant (normally a lieutenant-commander) is appointed as his deputy. The post of first lieutenant in a shore establishment carries a similar responsibility to the first lieutenant of a capital ship.
Within the British police, inspector is the second supervisory rank. It is senior to that of sergeant, but junior to that of chief inspector. The rank is mostly operational, meaning that inspectors are directly concerned with day-to-day policing. Uniformed inspectors are often responsible for supervising a duty shift made up of constables and sergeants, or act in specialist roles such as supervising road traffic policing.
The rank of inspector has existed since the foundation of the Metropolitan Police, formed in 1829, when it was used to designate the rank immediately below that of superintendent, and many Commonwealth police forces also use the term.
Plain-clothes detective inspectors are equal in rank to their uniformed counterparts, the prefix "detective" identifying them as having been trained in criminal investigation and being part of or attached to their force's Criminal Investigation Department (CID).