Poor Boris Johnson.

In January, the flight of fancy-prone U.K. foreign secretary floated a grand idea: a bridge that would span 22 miles across the English Channel linking England and France. Keep in mind that as former mayor of London, Johnson is most known for his legacy of design blunders, wildly expensive vanity projects and things that no one really wants or uses.

And so, somewhat predictably, Johnson’s latest headline-grabbing non-starter was scoffed at and quickly waved off. One French minister called it "far-fetched" — a sentiment that was largely felt across the board. After all, Johnson, no stranger to widespread ridicule, doesn’t have the greatest history with bridges.

Boris Johnson

But Johnson can take a wee bit of credit for sparking the idea for another lengthy landmark bridge that some politicians are throwing their support behind.

Pitched by prominent U.K. architect Alan Dunlop in direct response to Johnson’s mostly mocked bridge idea, this decidedly more warmly received bridge concept involves a road/rail crossing that spans 25 miles across the North Channel of the Irish Sea to connect Scotland with Northern Ireland.

According to Dunlop, who is also a professor at the University of Liverpool’s School of Architecture, this so-called "Celtic Connection" would be dramatically less expensive to build than an English Channel Bridge (roughly 15 to 20 billion pounds) while benefitting the economies of both Northern Ireland and Scotland. What’s more, Dunlop’s bridge would be far less complicated from a logistics standpoint.

"We don't have the weather problems and it is not as significant or as large a shipping lane, Dunlop tells the BBC. "The possibilities of it are great. It would send out a dramatic marker in aspiration for the country going into the 21st century."

Speaking to John Beattie of BBC Radio Scotland, Dunlop goes on to call the potential connection "a wonderful thing."

"We share a lot of history together, similar ideals," he says. "The business potential is exceptional, the chance of actually really making an investment in what would be the true north."

Presently, traversing the North Channel (formerly the Irish Channel) requires a ferry ride on one of two lines that make multiple crossings per day (the voyage lasts between two and three hours) or a quick plane ride. Some brave souls prefer to swim.

Portpatrick, Scotland In Great Britain, the conceptual span's terminus would be in or near Portpatrick, a Scottish village situated on a hammer-head peninsula known as the Rhins of Galloway. (Photo: Wikimedia Commons)

The not-so-minor radioactive waste issue

As for where exactly this theoretical bridge might be built, Dunlop imagines that it most likely would link Portpatrick, a village perched on the southwestern Scottish coast in Dumfries and Galloway, with Larne, a seaport in County Antrim, Northern Ireland. An even shorter passage in a different locale — a roughly 12-mile stretch between Scotland’s Mull of Kintye and the Antrim coast — could also be a possibility. But as Dunlop points out, even though the bridge in the latter scenario would be shorter, on both ends the span would terminate in rugged, remote areas with little to no existing transportation infrastructure. In the first scenario, the bridge would be about twice the length but easier to connect with major roads and rail lines.

Per Dezeen, one major challenge involved with building a North Channel bridge in either spot is getting around Beaufort’s Dyke, a 2-mile-wide, 31-mile-wide deep sea trench-cum-radioactive waste graveyard off the Scottish coast that was used as a dumping ground for chemical munitions following World War II. Presenting a significant engineering challenge, the presence of the trench makes any sort of bridge — or tunnel, for that matter — a whole lot less feasible.

Noting that "Britain’s toxic legacy is preventing Scotland from developing its full potential," Wee Ginger Dug, a columnist for Scotland’s The National, writes:

One of Scotland’s major roles in the U.K. is as a dumping ground for waste and as a host for nuclear weapons. The cost of cleaning up the seabed and removing Britain’s military waste is likely to run into untold millions of pounds. The MoD [Ministry of Defence] claims that there is ‘no evidence’ that the waste is harmful as long as it is left undisturbed. But there’s only no evidence because no one has looked for it.

However, Dunlop notes that a potential workaround to this specific area could be to incorporate floating bridge technology. While floating bridges that accommodate vehicular traffic most certainly exist and have for decades, floating rail lines do not. However, Washington state, where floating bridges can already be found in relative abundance, is working on it. (The Homer M. Hadley Memorial Bridge, one of the two Interstate 90-carrying floating bridges that cross Lake Washington between Seattle and Mercer Island is having its reversible HOV lanes converted into train tracks for light rail. The massive, congestion-relieving retrofit is due to be completed by 2023.)

Øresund Bridge, Denmark/Sweden Linking the Danish capital of Copenhagen with Malmö, Sweden, the Øresund Bridge is an example of a country-spanning rail and road bridge done right. (Photo: News Oresund/flickr)

Scandinavian inspiration

Although it doesn’t involve pontoons, the Øresund Bridge, a game-changing cable-stayed bridge-tunnel combo that carries both rail and motor vehicle traffic over and beneath the Øresund Strait between Sweden and Denmark, served as a key inspiration for Dunlop’s Great Britain- and Ireland-linking concept.

"The Oresund Straight bridge has brought huge economic and social benefits to Denmark and Sweden, creating a new economic region of almost 4 million people and generated £10 billion economic benefits to both countries," Dunlop tells Dezeen. "Such a bridge could do the same for Scotland and Ireland, economically, culturally and socially and boost tourism."

While both Scotland, located on the island of Great Britain, and Northern Ireland, which comprises the northeastern part of the island of Ireland, are countries within the United Kingdom ("country" can be tricky when describing the latter), bridges that cross international borders are relatively rare. The Øresund Bridge is perhaps the most well known. Other country-linking spans include the Ambassador Bridge (United States and Canada), the New Europe Bridge (Bulgaria and Romania) and the Victoria Falls Bridge (Zimbabwe and Zambia). Completed in 2007, the Three Countries Bridge is an 813-foot pedestrian- and cyclist-only affair that links France, Germany and (almost) Switzerland.

'Entirely feasible' or an overpriced pipe dream?

As mentioned, Dunlop’s North Channel rail and road link concept has managed to garner genuine interest from politicians and the public alike.

Sammy Wilson, a senior parliamentary member with Northern Ireland’s Democratic Unionist Party (DUP), has thrown his support behind the idea, noting that a bridge would be economically advantageous to both countries and, for commuters and tourists, a much-welcomed alternative to costly ferry crossings.

"People used to think the Channel tunnel was pie in the sky," Wilson tells the Belfast News Letter. "This idea of a fixed crossing has been derided as nonsense for years, but it is entirely feasible from a technical point of view."

He notes that while exciting, such a project would likely rank low on a list of government priorities. The cost of such an endeavor would also likely be problematic and initially require significant private investment.

Naturally, a plan of such ambition has been greeted by a fair amount of skepticism (but minus the Johnson-level ridicule). Critics agree that the bridge could work but that geology, politics and all-important funding are all formidable obstacles that most likely cannot be overcome.

"Big infrastructure projects can be transformative," economist George Kervan tells the BBC. "But the trouble with this one is just the costs will kill it."

Still, many, including Northern Ireland’s former Economy Minister Simon Hamilton, are opting to don rose-colored glasses.

"Imagine being able to board a train in Belfast or Dublin and be in Glasgow or Edinburgh in just a few hours," he tells the Belfast Telegraph. "It would revolutionise our trade and tourism, never mind our sense of interconnectedness. It maybe isn't as unrealistic an idea as you'd first think."

Boris Johnson inset photo: John Thys/AFP/Getty Images

Matt Hickman ( @mattyhick ) writes about design, architecture and the intersection between the natural world and the built environment.