But, even if this is so, it does not mean the work of the royal commission can or should be dismissed. The question of the extent to which corrupt individuals and practices infect the trade union movement is of vital public importance – precisely because unions play such an important role in Australian society. However, it is precisely because of the importance of this inquiry that any possibility of bias must be removed. Illustration: Andrew Dyson From what we know, Heydon accepted, in good faith, what he believed to be an invitation to deliver an apolitical speech to members of the NSW Bar Association. My understanding is that the event was open to any member of the NSW bar – irrespective of their political persuasions. The fact that the lecture is named in honour of an iconic Liberal Party lawyer and politician, Sir Garfield Barwick, should not have been taken as evidence of political bias, as Barwick's importance to the law extends well beyond any measure that can be reduced to a matter of mere party affiliation. Instead, it seems the organisers of the event betrayed Heydon's good intentions by not adequately disclosing to him that the occasion is, in fact, a fundraising opportunity for the Liberal Party – as the printed invitation makes clear. Given that he was a sitting royal commissioner, there was a clear obligation on the organisers to make the nature of the event abundantly clear to Heydon, rather than rely on him to open an attachment to the email he was sent.

Immediately upon being alerted to the relevant facts, Heydon withdrew from the event. His response was entirely proper. However, we are still left to ask if, despite this, the Liberal Party has rendered Heydon's position as royal commissioner untenable? For example, should there be a form of "strict liability" that governs the position of a royal commissioner such that he or she is bound to resign their commission if perceived to have been compromised? Or do intentions matter most? Blameless as he undoubtedly is, Heydon has been placed in an invidious position. Given the political storm that has broken, it is reasonable to assume a large number of Australians will have assumed the worst. Because of the considerable controversy surrounding political donations and fundraising events, the mere suggestion that a royal commissioner should be involved in such events will carry the taint of scandal. This is damage of a kind that can rarely be undone by a denial of culpability – even when that denial is entirely truthful. Given this, the key question becomes: does the integrity of an individual (Heydon) outweigh the public interest in maintaining the highest levels of trust and confidence in the institution of a royal commission? This is not a novel question. Judges are routinely (if infrequently) required to decide if they should recuse themselves in cases where there is a perception of bias. If that perception is insurmountable – and especially if linked to facts, such as the fundraising invitation to the Barwick lecture – then that is typically the course of action a judge will take. In some regards, the standards applied to a royal commissioner are even higher, as the scope of their authority is wider than that of a judge. Indeed, Heydon has argued, in his own judgments, that the mere perception of bias should lead to a judge being disqualified from hearing a case in which this concern arises. In a 2011 High Court judgment, he wrote: "It is fundamental to the administration of justice that the judge be neutral. It is for this reason that the appearance of departure from neutrality is a ground of disqualification."

Blameless as he undoubtedly is, Heydon has been placed in an invidious position. "It is the perception of the hypothetical observer that is the yardstick," Heydon declared. It is Heydon's own reasoning that provides the answer to the question of what he ought now do. He must now distinguish his case from all others in which his earlier judgment has been applied. In doing so, he will have to convince all future witnesses not to seek, in each case, for the commissioner to recuse himself on the basis of apprehended bias. If Heydon cannot make a convincing argument, then the burden of this issue will fall on him to resign. That will then leave the federal government to work out how best to salvage the work of the Royal Commission into Trade Union Governance and Corruption – brought undone not by Labor but by the Liberal Party itself. I believe the first act of the Prime Minister, on behalf of the party he leads, should be to extend a profound apology to Dyson Heydon. Dr Simon Longstaff is executive director of the Ethics Centre (ethics.org.au), an independent, not-for-profit organisation focused on the promotion and exploration of ethical questions.