Assistant Commissioner of Police of the Metropolis

The rank of assistant commissioner was introduced by the Police Act 1856, which abolished the two joint commissioners and established a single Commissioner (Sir Richard Mayne) assisted by two assistant commissioners. The Assistant Commissioner (Administrative) was in charge of administration and discipline. The Assistant Commissioner (Executive) was in charge of executive business, supplies and buildings. The first two men to fill these posts were Lieutenant-Colonel Douglas Labalmondière and Captain William C. Harris respectively.

Like the Commissioner, the assistant commissioners were sworn in as justices of the peace, although they could not try criminal cases. This continued until 1973. Like the Commissioner, the assistant commissioners were mainly appointed from outside the police until well into the 20th century, although career police officers could and sometimes did rise to the rank.

In 1878, Howard Vincent was appointed Director of Criminal Intelligence, a post that had equal rank to the assistant commissioners, but not the title. On his resignation in 1884, his post was replaced by a third assistant commissioner, the Assistant Commissioner (Crime).

In 1909, Commissioner Sir Edward Henry, realising that the assistant commissioners' workload was becoming too great, appointed a fourth assistant commissioner, who took over some of the duties of the Assistant Commissioner (Executive). The four became known as Assistant Commissioners "A", "B", "C" and "L", heading departments with the same letter designations. Assistant Commissioner "A" effectively acted as Deputy Commissioner until 1931, when a separate Deputy Commissioner was appointed. From 1922 until 1931, Assistant Commissioner "A" was generally known as the Deputy Commissioner.

After World War I, Assistant Commissioner "B" became responsible solely for traffic and lost property, with his other former duties divided between Assistant Commissioners "A" and "L". Assistant Commissioner "L" was responsible for "L" (Legal) Department until its reorganisation in 1931. After 1931, he was renamed Assistant Commissioner "D" and became responsible for policy and planning.

By the end of World War II, Assistant Commissioner "A" (Operations and Administration) was responsible for all uniformed police, including specialist units, except traffic police, which were under Assistant Commissioner "B" (Traffic). Assistant Commissioner "C" (Crime) headed the Criminal Investigation Department (CID), and Assistant Commissioner "D" (Personnel and Training) was responsible for recruitment, training, welfare, communications and police dogs. In 1970, Commissioner Sir John Waldron designated Assistant Commissioner "D" as the senior Assistant Commissioner. As policing became more technical, Assistant Commissioner "B" also became responsible for technical support.

In 1985, Commissioner Sir Kenneth Newman finally abolished the system of lettered departments. He redesignated the four Assistant Commissioners as:

• Assistant Commissioner Territorial Operations (ACTO), in charge of all uniformed and CID units based on the divisions.
• Assistant Commissioner Specialist Operations (ACSO), in charge of all specialised and centralised uniformed and CID units.
• Assistant Commissioner Personnel and Training (ACPT), in charge of all personnel issues, including recruitment, training and welfare.
• Assistant Commissioner Management Support (ACMS), in charge of strategic planning, management services, public relations and a number of other miscellaneous departments.

In 1992, with increasing focus on the Met's image and quality of service, Commissioner Sir Peter Imbert redesignated the ACMS as Assistant Commissioner Inspection and Review (ACIR), in charge of collecting performance data from across the Metropolitan Police District.

In 1995, Commissioner Sir Paul Condon introduced the widest-ranging reorganisation when he increased the number of assistant commissioners to six. The previous eight Areas, each commanded by a deputy assistant commissioner (DAC), were reduced to five, each commanded by an assistant commissioner, designated AC 1 to 5. Each assistant commissioner also had force-wide responsibility for a 'portfolio' (such as crime or traffic), setting force policy and managing related headquarters branches. ACSO remained outside the area system and continued to manage the Specialist Operations units.

In 2000, the system changed again, with policing restructured around the boroughs and the areas being abolished. The six assistant commissioners were reduced to four again. With the creation of the Specialist Crime Directorate under its own assistant commissioner in 2002, there were five assistant commissioners, although this was once again reduced to four in 2008. In 2011, the number was briefly increased to five again, then reduced to four once more. The posts have held varying designations since 2000, with the ACSO being the only post to have remained since the initial reorganisation in 1985.

The assistant commissioners are considered to hold equal rank to the chief constables of other British police forces and wear the same rank insignia: a crown over crossed tipstaves in a wreath.

These positions existed concurrently.

These were not all concurrently existing positions.