Controversy has raged ever since it emerged the Opera House was going to be used to help promote The Everest, which is billed as the world's richest turf race and is a massive drawcard for tourism in NSW.
The protest is in response to the NSW government's decision to override an earlier ruling by the chief executive of the Opera House, Louise Herron, who did not want to project horse names and branding on the building's sails.
The forecourt and surrounding areas of the Opera House were packed with onlookers and people looking to make a stand against the use of the building to promote race colours, barrier draw numbers and The Everest Trophy for the lucrative event.
However, in a dramatic turn today, Racing NSW suspended all betting for the $13 million race from noon and announced the barrier draw would be conducted in confidence.
Racing NSW said the decision to draw the results prior to tonight's event was "to circumvent any security risks that may exist".
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An online petition has gathered more than 250,000 signatures in a bid to "save" the Opera House from commercialisation.
In a letter to the premier on Tuesday, the NSW Heritage Council said it was extremely disappointed with the government's decision and described the projection as "inappropriate".
Activist group Sleeping Giants Oz is targeting Alan Jones advertisers, accusing the 2GB host of bullying Opera House CEO Louise Herron into allowing advertising to be projected onto the iconic landmark.
Mr Greenwich said he would move a motion in parliament to amend the Sydney Opera House Trust Act to "stop the culture of a minister picking up the phone on behalf of his mates in the racing industry and telling the Opera House what to do".
"So to Louise and those people who've been offended, I apologise".
Mr Quint said the legal exemptions allowing projection onto the sails made clear that they must be "non-commercial occasions of brief duration".