Occasionally, as the bridge curved, you could just glimpse what looked like a giant millipede stepping across the water in the foggy distance. Just recently, the world’s longest sea-crossing opened for business and I was one of the first to make the trip. The light was a little murky; sea and sky had melded so that it looked as if the Chinese fishing-boats, with their nets akimbo, were flying through the air. Autumn in Hong Kong is the season when the winds change direction and the north-east monsoon begins to blow pollution down from the factories on the Pearl river delta.

The Hong Kong-Zhuhai-Macau Bridge (HZMB) is intended to stitch together the two former colonies of Hong Kong and Macau (one British; one Portuguese) with the coastal Special Economic Zone of Zhuhai and create part of an even bigger tapestry: the Greater Bay Area. China says it will promote economic strength and efficiency. To critics, the bridge is an excuse to fold Hong Kong into the mainland until it disappears.

Whatever the reason, after years of complaints over the cost (about Dh74.7 billion), when China announced that the bridge would finally be inaugurated by President Xi Jinping in Zhuhai last month, it gave less than a week’s notice. Slightly inauspiciously, the news came on October 17, a grave-sweeping public holiday in Hong Kong.

Inauguration, it turned out, did not mean open for business. Those who wanted to be at the head of the queue to cross would have to wait another day when the public would at last be able to get a first-hand sense of a project officially begun in 2009.

Although the HZMB is described as 55km long, much of that consists of access roads. The actual distance it crosses the sea is 30km, and it’s not continuous

Not that there was much of a queue. After all the hype, crossing this exceedingly expensive political symbol turned out to be the smoothest, and least crowded, excursion I’ve ever done in Hong Kong.

The gateway to the bridge is about five minutes’ journey from Hong Kong airport and inside the passenger clearance building, with its wavy roof designed to resemble the sea beyond, people ambled about, sparsely, and a long row of immigration officers sat waiting for business. Three staff helped with the purchase of my shuttle-bus ticket.

I decided to test the Macau route – of more interest to visitors than Zhuhai which, as part of China proper, means getting a visa. I love Macau and if you don’t mind the hike to the port, the bridge certainly makes getting there cheaper: instead of an hour-long ferry journey costing about Dh82, the road trip takes just 35 minutes and costs about Dh31. Once there visitors will be able to experience an astounding contrast of casinos and churches and savour the genuine traces of Portuguese heritage.

We set off, briskly, on the right-hand side of a dual, three-lane carriageway. Both Hong Kong and Macau, as former colonies, are left-hand drive. Zhuhai is not. And because the bridge crosses mainland water, the characters on the road signs suddenly switch from traditional on blue background (Hong Kong) to simplified on green background (China), then back to traditional on blue (Macau).

While I’m being pernickety about details: although the HZMB is described as 55km long, much of that consists of access roads. The actual distance it crosses the sea is 30km and it’s not continuous. It dives into a tunnel for 6.7km to allow shipping to pass overhead. Still, it’s an extraordinary engineering feat, which is why I and my fellow passengers were devoting a day’s outing to it.

There was almost no traffic; coasting through miles of empty space added to the novelty of the experience. At the Macau end, the vast building – its lovely filigreed facade glowing in the late-afternoon sun – was almost deserted.

On the return journey, the sky cleared and all the billowing hills of Lantau island took on an almost-Celtic verdancy I’d never noticed before. Go soon.

discoverhongkong.com; macautourism.gov.mo