In sentencing Williamson to 7½ years in jail with a five-year non-parole period, District Court Judge David Frearson said his actions were ''a parasitic plundering of union funds for pure greed''.

''[It was] a reprehensible betrayal of the union and all its members,'' he said.

The frauds were calculated, brazen and arrogant and involved an ''extreme'' breach of trust, he said.

But what Williamson has been jailed for was only the tip of the iceberg. He had been defrauding the union for almost two decades.

Williamson, who ran the HSU as his personal fiefdom from 1995 to 2011, pleaded guilty to several counts of defrauding the union of close to a $1 million and enlisting family and friends to cover up his crimes.

One time, Williamson claimed thieves had broken into the safe in his office and stolen thousands of dollars. At the same time someone using Williamson's card accessed the building. He declined to report the matter to police.

He was reimbursed three times by the union after claiming he had been mugged at an ATM.

Among those at court was Paul Ford who, with Mark and Janice Hardacre and others, ran against Williamson for control of the union in 1999.

They discovered he had an HSU-issued American Express card that he used for Chanel perfume, jewellery, restaurant bills, a $1045 David Jones bill, Clinique skin care products worth $105, valet parking, a gas bill, and designer handbags. He responded by filing a $750,000 defamation suit against them.

Outside court Mr Ford said: ''Those who supported and enabled him should also be held accountable. We want our $25,000 returned, especially to the family of the late Bill O'Connor.''

He said Mr O'Connor was a 76-year-old pensioner at the time he had to pay $25,000 for pointing out Mr Williamson was corrupt.

Mr Ford was also angry with the NSW Labor Party ''who knew about this but still promoted Williamson''.

About the time of the defamation action, Williamson asked the union's printers, John and Carron Gilleland, to supply him and later his protege Craig Thomson with American Express cards, mentioning it would help avoid scrutiny of union election expenses. This might have constituted a secret commission, a jailable offence.

Strike Force Carnarvon was formed in 2011 after Fairfax Media revealed the existence of the cards.

Williamson then instructed the Gillelands to destroy any American Express card statements. They refused and assisted police.

But police soon found a paucity of financial records to pursue criminal charges. Instead that found an extraordinary array of other corrupt dealings.

There was Canme, a family company Williamson used to bill the union for more than $300,000 by falsely claiming his wife was doing archiving work, backed by false invoices.

He also pleaded guilty to corruptly receiving $600,000 in cash from December 2006 to February 2010 by getting a supplier to the union, Alf Downing, to inflate his prices.