The distinctive shape of the Sydney Opera House, with its billowing sails, is to be protected by trademark, in a legal landmark for an Australian building.

The move will prevent souvenir shops from exploiting the widely recognised silhouette of the World Heritage-listed building overlooking Sydney Harbour for commercial purposes.

The Opera House, which celebrated its 40th birthday last year, has become increasingly protective of its unique selling points. Its logo and two-dimensional image are already trademarked, while its three- dimensional shape - as seen from all angles - will be registered next month unless an objection is lodged and upheld.

So anyone planning to cash in by producing cheap mugs or key-rings based on those famous sails had better hurry. From March 23, no one except the Opera House will be able to market souvenirs, unless they pay a fee to do so.

Advertisement

The official range of gifts includes a Lego replica consisting of nearly 3000 pieces and featuring "advanced building techniques for complex forms, angled walls and subtle detailing", standing 25cm high and retailing at A$399.99 ($437.60).

One patent lawyer, Mark Williams, told the Australian that it was the first building he knew of to be trademarked in Australia. Most were not distinctive enough to warrant it, he said.

Last year, in another unusual move, the Sydney Opera House commissioned Deloitte Access Economics to put a dollar value on it as a public asset. The accountancy firm came up with A$4.6 billion, taking into account everything from land value, ticket sales and tourism to more esoteric features.

The impact on tourism alone of the world's busiest performing arts centre, designed by Danish architect Jorn Utzon, was estimated to be equivalent to 8500 full-time jobs. Its value in cementing national identity was A$2 billion - a figure accountants hit upon after surveying more than 3000 people around the world.

The legal firm King & Wood Mallesons, which is one of the Opera House's corporate sponsors, said it was one of the world's most recognised images. "However, while it is a symbol of Australia and a great public institution, some people think that they can use the image for their own commercial purposes, or as part of their own brand," it added.

World Heritage-listed since 2007, alongside the Taj Mahal, pyramids and Great Wall of China, the Opera House has been key to the evolution of Australia's cultural identity.