The prince claimed that releasing 'intensely private and confidential material' would be a breach of his human rights.

By way of example, that could involve placing confidential material in an annex which the court could readily identify and order not to be disclosed.

Procedures for intercepting data since 2010, which allowed for spying on confidential material passed between lawyers and clients, have not met human rights safeguards, it said.

The court, exercising its inherent power in controlling its own procedures developed the law relating to public interest immunity to decide the scope of disclosure in cases involving confidential material.

Many companies remain concerned about how much a worker, given full director rights, would be paid and what access to confidential material would be feasible.