Undercover policing is the lifeblood of many dangerous and sensitive investigations. The evidence that's obtained in these operations can bring intelligence of the highest quality ? and it can lock up dangerous people. That's all to the good. But it also involves deceit and intrusion on a grand and perhaps growing scale, sometimes practised on those caught up in things they have no responsibility for and don't understand. So getting this balance right, between the effectiveness of undercover work, and its accompanying abuses of privacy and intimacy, must be the key to public confidence.

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