Special Investigation Branch

Special Investigation Branch (SIB) was the name given to the detective branches of all three British military police arms: the Royal Navy Police, Royal Military Police and Royal Air Force Police. It was most closely associated with the Royal Military Police, which had the largest SIB. SIB investigators usually operated in plain clothes, although they did wear uniforms when serving overseas. Members were usually senior non-commissioned officers (sergeants or petty officers or above) or commissioned officers, although the Royal Air Force SIB was open to corporals and Acting Corporals. In December 2022, the new tri-service Defence Serious Crime Unit replaced all three service SIBs. All staff retain their own single service trades and identities, but now work within one combined unit.