Starting at page 648 Jessel M.R said,

What is the rule, and what is the meaning of the rule?

…The object and meaning of the rule is this: that as, by reason of the complexity and difficulty of our law, litigation can only be properly conducted by professional men, it is absolutely necessary that a man, in order to prosecute his rights or to defend himself from an improper claim, should have recourse to the assistance of professional lawyers, and it being so absolutely necessary, it is equally necessary, to use a vulgar phrase, that he should be able to make a clean breast of it to the gentleman whom he consults with a view to the prosecution of his claim, or the substantiating his defence against the claim of others; that he should be able to place unrestricted and unbounded confidence in the professional agent, and that the communications he so makes to him should be kept secret, unless with his consent (for it is his privilege, and not the privilege of the confidential agent), that he should be enabled properly to conduct his litigation. That is the meaning of the rule.

Now, as to the extent of the rule. It goes not merely to a communication made to the professional agent himself by the client directly, it goes to all communications made by the client to the solicitor through intermediate agents, and he is not bound to write letters through the post, or to go himself personally to see the solicitor; he may employ a third person to write the letter, or he may send the letters through a messenger, or he may give a verbal message to a messenger, and ask him to deliver it to the solicitor, with a view to his prosecuting his claim, or of substantiating his defence.

Again, the solicitor’s acts must be protected for the use of the client. The solicitor requires further information, and says, I will obtain it from a third person. That is confidential. It is obtained by him as solicitor for the purpose of the litigation, and it must be protected upon the same ground, otherwise it would be dangerous, if not impossible, to employ a solicitor. You cannot ask him what the information he obtained was. It may be information simply for the purpose of knowing whether he ought to defend or prosecute the action, but it may be also obtained in the shape of collecting evidence for the purpose of such prosecution or defence. All that, therefore, is privileged.

Then the rule goes a step further. The solicitor is not bound any more than the client to do this work himself. He is not bound either to collect information or to collect testimony. He may employ his clerks or other agents to do it for him, and upon the same principle as the information acquired by himself directly is protected, so the information acquired by a clerk or agent employed by him is equally protected.

But then the cases go still a step further. Suppose the information required is in a foreign country, where neither the solicitor nor his clerk nor an ordinary agent can obtain it, he may request the client to obtain it himself, and then the information so obtained by the client at the request or under the advice of the solicitor is in a sense obtained by the agent of the solicitor, although it is a very odd way of expressing it. It is turning the client, so to say, into the agent of the solicitor for the purpose of obtaining information; but it is clearly within the rule of privilege. So far as I understand, the cases in equity go no further…

…Our law has not extended that privilege, as some foreign laws have, to the medical profession, or to the sacerdotal profession. We know that in some foreign countries communications made to a medical man are privileged, upon the ground that it is as desirable that a man shall be perfectly free in his communication with *651 his medical man as that he shall be free in his communications with his lawyer. That has not been recognised in this country. Again, in foreign countries where the Roman Catholic faith prevails, it is considered that the same principles ought to be extended to the confessional, and that it is desirable that a man should not be hampered in going to confession by the thought that either he or his priest may be compelled to disclose in a Court of Justice the substance of what passed in such communication. This, again, whether it is rational or irrational, is not recognised by our law…

Edited for ease of reading.