A Counter-Terrorism Specialist Firearm Officer (CTSFO) is a United Kingdom police frearms officer. The CTSFO standard is currently the highest level of Authorised Firearms Officer in the National Police Firearms Training Curriculum. It was established by the Metropolitan Police Service (MPS).
The MPS have established the Specialist Firearm Command (SCO19), which has seven teams of CTSFO officers within it. They are commonly depicted with identification patches on the upper arm, which includes their team number, alongside the bottom leftmost corner being a colour dependant on their team.
CTSFOs are equipped with the Sig Mcx.