Warrant officer
In the British Army, there are two warrant ranks, warrant officer class 2 (WO2) and warrant officer class 1 (WO1), the latter being the senior of the two. It used to be more common to refer to these ranks as WOII and WOI (using Roman instead of Arabic numerals). Warrant officer 1st class or 2nd class is incorrect. The rank immediately below WO2 is staff sergeant (or colour sergeant).