One of Sydney's most iconic bridges, the Gladesville Bridge in the city's inner-west is celebrating 50 years.

The arch bridge crosses the Parramatta River between Huntleys Point and Drummoyne and is part of Victoria Road.

When it opened in October 1964, it was the longest concrete bridge in the world, measuring 579.5 metres.

It held that record until Croatia's Krk Bridge was built in 1980.

The huge arch-style might not have eventuated if it was not for a UK-based company in Australia trying to drum up business.

The UK firm submitted an alternative design to the Department of Main Roads.

Engineer Tony Gee was just 22-years-old when he was given the job to design the bridge.

Mr Gee said he was given the huge job because the firm thought it was a long shot and did not want to waste too much money.

"So they thought, 'who doesn't cost very much, let's get the recent graduate and send him down there'.

"No one had built a concrete bridge of that size before and that must have been a factor that they took into consideration."

Mr Gee told 702 ABC Sydney's Breakfast host Robbie Buck that the bridge's four ridges were built by four seperate construction teams.

Titan floating crane in use erecting deck beams for the roadway on the Gladesville Bridge (November 1963) ( Supplied: Roads and Maritime Services )

Enjoying the view was not a problem for the designer.

"The little office that we used to monitor and supervise the jacking was right up on top of the bridge, so if anything had gone wrong I would have gone down with it."

The bridge is still considered globally significant, said Mark Bennett, senior bridge engineer with Roads and Maritime Services.

"It's still right up there with major bridges around the world and it's a testament to the good quality construction and design that the bridge is still in excellent condition.

"Post-tensioning and pre-stressing of concrete was new technology at the time.

"The deck that you actually drive across was post-tension concrete girders," Mr Bennett said.

Not without controversy

The construction was supposed to be the centre of a much larger plan and after the bridge was built there was debate whether that plan should be followed.

"During the 1950s and 60s an extensive freeway network was being planned for the city.

"Gladesville Bridge and its northern approaches were to form part of the north western expressway heading up to Wahroonga where it would join with the Sydney-Newcastle expressway," said Vince Taranto from Roads and Maritime Services, who researches historic road and bridge projects.

That link never eventuated.

The construction also caused a bit of protest from concerned locals due to the demolition of historic residences in the area.

"It involved the demolition of a large number of properties and also some historic properties," Mr Taranto said.

The most notable of these was the mansion St Malo in Hunters Hill.

HRH Princess Marina, Duchess of Kent inspects Riverside Girls High School students forming the Guard of Honour (2 October 1964) ( Supplied: Roads and Maritime Services )

At the time of the construction the protocol to determine if there was too much rain to continue working on the bridge was to hold a cigarette paper up into the rain.

"The supervisor would walk out and if there was more than a few drops after a couple of seconds then that was it, work stopped," Mr Taranto said.

"So there was a very very high awareness of safety on the site and it's a great credit to the quality of supervision and dedication of the workers that there were no deaths or serious injuries during the project."

Will the bridge be here in another 50 years? Mark Bennett thinks so.

"Arches are inherently robust structures. The bridge appears to be in excellent condition still, so I'd be quite confident the bridge will still be here in 50 years," he said.

Sydney remembers

Many memories of the bridge came flowing into 702 ABC Sydney Breakfast from callers.

Judy from Balmain said she was attending Riverside Girls High School at the time the bridge was opened 50 years ago.

The school is on the approach to the bridge on the Gladesville side.

Judy remembers watching the opening procession from the playground.

"It was quite an exciting occasion, shoes had to be polished, the straw hats had to be all perfect. The rest of the school fraternity, all the other students were in the playground watching from there," she said.

Older girls from the school were chosen to form a guard of honour on the special day the bridge was opened by Princess Marina, Duchess of Kent.

Another caller, Graeme from Turramurra, said he remembers the previous bridge having no provision for pedestrians.

"There was an arrangement with the government bus company, so pedestrians could join a bus on either side of the bridge free of charge."

The bridge will be lit at night as part of its 50th anniversary celebrations.