Yesterday’s revelation that Justice Dyson Heydon accepted an invitation to attend a Liberal Party event that may or may not have been a fundraiser is a disaster for the Abbott government.

The former High Court judge, who was appointed by the Coalition to head the politically motivated Royal Commission into Trade Union Governance and Corruption, denies he knew the Sir Garfield Barwick Address was a party political event.

But justice relies on the perception of impartiality. Whether Heydon knew he had agreed to speak at a Liberal Party fundraiser or not is actually irrelevant. What is relevant that he accepted the invitation.

When a sitting judge or royal commissioner agrees to attend a public function run by the same political party that is employing him in a currently active (and politically controversial) royal commission, this destroys the public perception of that judge’s impartiality.

The result is that he is now perceived to be biased, and any of findings will be perceived to be tainted.

He should resign. Today.