What are the legal principles applicable to a motion for a further and better affidavit?

The parties agree on the legal principles applicable to a motion for a further and better affidavit (or list of documents) under rule 30.06. As D.M. Brown J. as he then was, noted in Leduc v. Roman 2009 CanLII 6838 (ON SC), [2009] O.J. No. 681: “the onus for reviewing documents to determine their relevance rests, in the first instance, with the party bearing the obligation to produce” (at para 14). Once one party suspects the opposite party has failed in this duty, that party may bring a motion. The motion requires actual evidence that potentially relevant undisclosed documents exist, as opposed to mere speculation.