When will disobedience to an instruction justify dismissal?

Employers have the common law right to issue a lawful and reasonable direction or instruction to an employee, who will ignore compliance with it at his or her peril.
But what constitutes such an instruction, which if not obeyed, can justify dismissal?
“The test of whether a direction is lawful and reasonable was stated by Dixon J in R v Darling Island Stevedoring and Lighthouse Ltd; Ex parte Halliday and Sullivan 4 in these terms:
“But the award could not safely, or, at all events, fairly impose upon the employees an obligation to obey all instructions given by employers…Some qualification or restriction was necessary. Naturally enough the award adopted the standard or test by which the common law determines the lawfulness of a command or direction given by a master to a servant. If a command relates to the subject matter of the employment and involves no illegality, the obligation of the servant to obey it depends at common law upon its being reasonable. In other words, the lawful commands of an employer which an employee must obey are those which fall within the scope of the contract of service and are reasonable…But what is reasonable is not to be determined, so to speak, in vacuo. The nature of the employment, the established usages affecting it, the common practices which exist and the general provisions of the instrument, in this case the award, governing the relationship, supply considerations by which the determination of what is reasonable must be controlled.”
In Woolworth Ltd v Brown 5 a Full Bench of the Commission observed as follows:
“In the modern era employers face an often bewildering array of statutory obligations in relation to matters such as health and safety, discrimination, taxation, trade practices and fair trading to mention the most obvious examples. Employers face potential liability arising from their common law duty of care to their employees and to members of the public. Employers may be subject to contractual obligations that require them to conduct their business in a particular way or to meet particular standards or observe particular constraints. For these reasons it is entirely reasonable, and often necessary, for employers to put in place policies, with which employees must comply, to facilitate the employer’s compliance with its obligations and duties. (at [24])

What is reasonable will depend upon all the circumstances including the nature of the employment, the established usages affecting it, the common practices which exist and the general provisions of the instrument governing the relationship. A policy will be reasonable if a reasonable employer, in the position of actual employer and acting reasonably, could have adopted the policy. That is, a policy will only be unreasonable if no reasonable employer could have adopted it. A policy will not be unreasonable merely because a member of the Commission considers that a better or different policy may have been more appropriate. As the Full Bench observed in the XPT case, albeit in a somewhat different context, it is not the role of the Commission ‘to interfere with the right of an employer to manage his own business unless he is seeking from the employees something which is unjust or unreasonable.’” (at [35]) 6
In Briggs v AWH 7 the Full Bench relevantly said (at [8]):
“The determination of whether an employer’s direction was a reasonable one … does not involve an abstract or unconfined assessment as to the justice or merit of the direction. It does not need to be demonstrated by the employer that the direction issued was the preferable or most appropriate course of action, or in accordance with “best practice”, or in the best interests of the parties. The proper approach to the task is that identified by Dixon J in The King v Darling Island Stevedoring and Lighterage Company Limited; Ex Parte Halliday and Sullivan.”
Whether a direction is reasonable is essentially a question of fact and balance. ”

Construction, Forestry, Mining and Energy Union v Glencore Mt Owen Pty Ltd (2015) FWC 7752 delivered 17 November 2015 per Saunders C