Steve Tsoukalas has been having an affair for more than four decades and while he's still desperately in love with his "mistress", his wife doesn't mind a bit.

The "other woman" in Steve's life is Sydney Opera House, and taking a stroll around the iconic building he constantly refers to it as "the lady".

And at 40 years of age she's still drop dead gorgeous, never failing to catch the admiring eye of those who pass her.

"She's a beautiful old lady, but that lady is my mistress, my lover. I love her and I've got my beautiful wife at home for 45 years," he said.

Steve's love affair began on the day he sailed into Sydney Harbour as a Greek immigrant in 1964.

He recalls seeing the scaffolding and cranes at Bennelong Point and thought it looked like something from outer space as 5,500 planks covered the billowing sails, soaring 55 metres above the harbour.

By 1968 he was getting up close and personal with the lady.

In the same year he married, he'd got a job supplying scaffolding for the structure.

He joined a multicultural workforce of new Australians who, he says, were occasionally mocked because of their heritage.

But this only strengthened the bond between them as they worked to build a monument to modern Australia.

There were strikes. Earning just $60 a week, the workers had to fight for sick pay.

Yet Steve saved enough to fulfil his dream to start a family and buy a house in Sydney's southern suburbs for $12,500. He has two sons, an economist and a medical scientist.

"I thank the Australian people and I thank this beautiful lady because they gave me the opportunity to educate my family and to educate myself," he said.

Five years after joining the Opera House workforce, Steve's job was done.

Opera House's secret beauty regime revealed

The building was complete, when many had thought the work of art would never be finished.

His friends picked up their tools and moved to the next building project. But Steve couldn't leave.

Bennelong Point had become a second home and he soon established himself as an indispensible member of the Opera House family.

With more than one million tiles, and a structure exposed to the harsh elements of sun and saltwater, the building requires constant cleaning and maintenance.

Steve Tsoukalas stands beside his 'mistress'. ( ABC News )

Steve has for years been lavishing love and attention on the house like a hopelessly infatuated admirer.

After a little experimentation he came up with a beauty regime, which gives away his Greek origins. He mixes olive oil with a splash of methylated spirits to clean the bronze doors, railings and other fittings.

It's a recipe that was approved by the building's late designer Jorn Utzon. For the exposed concrete Steve uses baking soda to wipe away the city grime.

"For many years they tried different ways. They thought it was a joke to use olive oil," he said.

On the steps of the Opera House Steve is embraced by a tall and urbane, grey-haired man. Jan Utzon, architect and son of the man whose vision is realised before them, is well aware of Steve's life-long devotion to the building.

He's effusive in his praise for the Australian and hopes he can continue his work.

But Steve is now in his mid-60s and retirement is not far away.

Contemplating life away from the lady is difficult.

"I try to reject the word retirement because I feel emotional and I don't want it to come the time, never.

"If you marry the same year you start here and you're in love with two beautiful ladies it's not easy to leave one. Happy Birthday my darling, I love you."