In his letter, Jon Mack may have misunderstood Ibrahim Hasan’s article of 10 March on directed surveillance.

The focus of the piece was changes in the law now proposed, namely judicial approval, which is already the subject of the Protection of Freedoms Bill and the serious offence test for directed surveillance.

Article 8 of the European Convention on Human Rights, which is the human right to respect for one’s private and family life, includes the right to establish and develop relationships.

Accordingly, any manipulation of a relationship by a public authority for a covert purpose is likely to engage article 8.

That is why you need a Regulation of Investigatory Powers Act authorisation, so that it is lawful ‘for all purposes’.

Local authorities have been known to place ‘dummy’ families into a house on an estate, to engage with the other residents and observe anti-social behaviour in situations where the real residents who could be witnesses refuse to give evidence through fear of reprisals.

This fear arises precisely because they are known to the perpetrators.

Those undercover officers are also witnesses.

They have entered the estate for the covert purpose of entering into a relationship or relationships with people on the estate and to obtain information covertly from those relationships.

Why are these witnesses not ‘witnesses on a housing estate disclosing information about anti-social behaviour’?

Shelagh Lyth, solicitor and consultant, Parry Welch Lacey, Rossendale, Lancashire