The letter also raised concerns over a 2023 National Physical Laboratory study, which found the NeoFace system used by the Met was less accurate for women and people of colour depending on the algorithm that has been set. The study's authors found the system could show bias at lower thresholds, though at the higher settings the Met says it uses, performance was found to be equitable across ethnicity and gender. These thresholds are confidence levels the system uses to decide a match - lower ones flag more people but risk more mistakes and bias, while higher ones are stricter and more balanced. Campaigners said there was no legal obligation for the force to avoid the lower thresholds, and argued policing resources would be better spent on safety measures at the carnival. Deputy Assistant Commissioner Matt Ward, who is leading this year's policing operation at the carnival, said LFR had led to more than 1,000 arrests since the start of 2024 and that independent testing showed the system was "accurate and balanced with regard to ethnicity and gender" at the thresholds used by the Met.