What is the test for a solicitor to sue for liens over documents?

The facts of the Balch v. Symes case are not the standard stuff of claims by solicitors for liens over documents. Apart from the procedural elements involving the production of documents in litigation, the case involved a claim that the solicitor had committed a fraud on the client – hardly the facts upon which to lay down a principle of general application. Further, the Lord Chancellor confined his reasoning to a case where a solicitor possessed the current will of a living client, arguing that since a client might wish to change her current will, a solicitor could not refuse to produce the original to her for alteration.