What is the test for reasonable diligence on a third arbitrator?

A precise contractual or judicial definition of "reasonable diligence," need not be delineated to perceive that appellant's claim should be barred because of his delay. While the reason for the one-year delay after the neutral arbitrator was finally appointed is unclear, appellant had the duty at all stages of the proceedings "to use due diligence to expedite his case. (Martin v. Cook (1977) 68 Cal.App.3d 799, 808, 137 Cal.Rptr. 434.) Appellant cannot in any case contend that he is being deprived of his day in court because of the neutral arbitrator's failure to set up a hearing, when appellant has been solely responsible for a three-year delay before the appointment of the third arbitrator.