In November 2003 Dutch Military Intelligence tortured dozens of prisoners in the Iraq province of Al Muthanna. Al Muthanna was under British command at the time. The Dutch did not have an official mandate to interrogate prisoners. Torture consisted of keeping prisoners awake by throwing cold water on them and the use of high-frequency noise and bright light. The venue was a complex of the Coalition Provisional Authority in As Samawah.
Later more. For the time being there is still a lot of denial and obfuscation. Dutch newspaper article here.