It's not easy to build a bridge and I can assure you as an engineer, that it's not easy to build the Harbour Bridge - a Through-Type Arch Bridge of significant proportions.

This is the defining monument for Sydney. One that we have come to affectionately refer to as "The Coat Hanger". And we have been proud to have "hung our coats" on it since 1932.

And the Bridge's similarities with that simplistic household item are unmistakable. It is reputed that no lesser than the Father of the American Constitution, President Jefferson had made the first coat hanger out of timber. The coat hanger has also filtered into the world of architecture, becoming the inspiration for the legendary Frank Lloyd Wright's award-winning Meyer May House in Grand Rapids.

But our beloved "coat hanger" is much more than that.

It is a triumph against diversity, having been built amidst the Great Depression. Over 1 km long and 134 metres above Sydney's stunning Harbour, it contains a staggering 53,000 tonnes of steel - enough to make 2.1 billion wire coat hangers. That's sufficient for every man, woman and child in China to "hang" two items of clothing each... staggering.

It also has over 6 million rivets and takes 272,000 litres of paint for one coat. That is enough to paint 81,600 houses in one year. This would be enough to solve Sydney's affordability crisis, if they could all be approved, built and painted in one year - a challenge we have not yet been able to master in Sydney.

So happy birthday Coat Hanger - many, many happy returns and don't let it worry you that you're on a Cricketer's Devil's Number of 87, because you are soon going to get a letter from Her Majesty Elizabeth Regina, to congratulate you on being a great servant to this Nation and reaching your Century.