Spath . . . I am aware of your preference for not just having a link as an answer, and had you asked the question I would have given you this precis:-
In England and Wales, the principle of legal professional privilege grants a protection from disclosing evidence. It is a right that attaches to the client (not to the lawyer) and so may only be waived by the client.
There are two forms of legal professional privilege:
1, Legal advice privilege protects confidential communications between lawyers and their clients for the purposes of giving or obtaining legal advice.
2. Litigation privilege protects confidential communications between lawyers, clients and third parties made for the purposes of litigation, either actual or contemplated.
The client must be sure that what he tells his lawyer in confidence will never be revealed without his consent. This fundamental right is recognised by English Common Law, and European Court of Human Rights, which has held it to be part of the right to privacy guaranteed by Article 8 of the Convention.
Privilege is absolute, in the sense that once it is established, it may not be weighed against any other countervailing public interest factor but may only be overridden expressly by statute.
Hope this helps?