For generations, Sydneysiders tumbled out of the pub, looked up at the Harbour Bridge and felt compelled to climb it, in the way that others are compelled to make a hat of a traffic cone. They used to be able to scale the gate, negotiate the spikes at the top, then go up the steps to the arch.

The legendary climber, Bryden Allen, did it the hard way. He squeezed into one of hangers from which the deck is suspended, climbed 200 feet up the inside (“rather like caving…great fun”), roping onto struts, until he got to the lower chord of the arch, where – in his estimation – the “real climbing” began. He had to stretch backwards to reach the lower lip, grip on rivet heads, let his feet fly out into space and force himself up onto the ledge with his arms, and once there, repeat the move on the upper lip six feet above him. “From there the climb [was] easy,” he reckoned.

A decade later, the French high-wire artist, Philip Petit, climbed the bridge one night, strung wires between the pylons and walked across them in the early morning in full view of the rush-hour traffic. The police were good-humoured about it, even when Petit continued performing by relieving one of his watch and tie; but they arrested him anyway and the court fined him $200.

By 2011, when the former soldier, Michael Fox, climbed the bridge to protest the custody laws, the fine had gone up to $3,000 and there was talk of three months in jail, but the judge might have seen the irony of a custodial sentence and left it at a fine.

The bridge is now watched by CCTV and patrolled by security guards and, in this jittery age, it is too easy to imagine a drunken prank being misread as a terrorist incident and some poor student being shot down from the arch by snipers.

But anyone with $228 (£140, US$170) to spare can now climb the bridge quite legally. Prince Harry’s done it, Oprah’s done it, and Usain Bolt, Katy Perry and Matt Damon. So have I.

The breathalyser seemed an unnecessary precaution at half-past ten in the morning, but the whole thing is organised like a commando assault.

Once the Climb Leader was satisfied that nobody was drunk, she handed us each a pair of overalls in BridgeClimb’s corporate colours and sternly warned us not to take anything out onto the bridge: not a camera, not a phone, not even a handkerchief. It seemed, again, a bit over the top, but then I suppose a dropped handkerchief could do plenty of harm if it draped itself over a motorcyclist’s visor.

We were allowed sunglasses, provided they were secured with a cord round the neck like your Grandma’s reading glasses; and there was an optional clip-on BridgeClimb cap for anyone who wanted to look more of a dick than they already did in the overalls.

Then, once we had gone through a metal detector to check that we had done as we were told, there was a training session to make sure we were familiar with steps and ladders – just in case we had reached adult life without using them. We were kitted out with harnesses and one-way radios and, as often in Australia, more or less forced to apply sun cream.

We went out in single file behind the Climb Leader, clipped into the lifeline and followed her up a series of service ladders, as the cars and the bikes and the trucks thundered past, through manholes, under stanchions, watching elbows and heads, until we came out on the top of the arch. Helicopters constantly buzzed the bridge, as if this really were the military exercise it felt like.

It was thrilling, in its way, but it is not really an adrenalin activity. There is no sense of danger. A clumsy person could probably twist an angle or even break a leg, but a clumsy person could break a leg walking to the shops. It is hard to see how someone could fall off the bridge by accident.

It is worth remembering that none of the 1,400 men who worked on the bridge between 1924 and 1932 used any protection at all, and only two of them fell off. They only had rivet heads as footholds, too: now there are steps welded into the arch. It is, in truth, more of a walk than a climb.

Nonetheless, it is quite something to see the business end of the bridge close up. You get a much better sense of its scale than you ever can from ground level. The Climb Leader told us that it was 440 feet above the harbour at its highest point, although to be annoyingly pedantic it is actually 440 feet above mean sea level. She also said that it was the longest single-arch bridge in the world, and apart from five others, it is.

The view silenced everyone: right across the harbour, over the Opera House, the Botanic Gardens, the Rocks, Circular Quay and the financial district beyond it, out east over Bondi Beach, north over Luna Park and Manly, and west towards the Blue Mountains. It is worth your $228.

We crossed over to the western side of the arch and walked back towards the south pylon, down the ladders and inside. I had lost all sense of time while I was out on the bridge. It felt like half an hour, perhaps an hour, had gone by but in fact it was three and a half.

© Richard Senior 2016