What is the test for service of documents in litigation?

The proper and valid service of documents involving litigation is fundamental to any further proceedings by which the litigation is advanced and imperative in order for a court to assume jurisdiction over the subject of the litigation. Such a fundamental concept was enunciated over half a century ago. It remains as valued today as it was when Lord Green, M.R. observed in Craig v. Klassen, [1943] 1 K.B. 256 at p. 262: It is beyond question that failure to serve process where service of process in required goes to the root of our conceptions of the proper procedure in litigation.