THE architect of the original plan to build a crossing to Northern Ireland has condemned Boris Johnson’s planned roundabout under the sea and claims it puts paid to any chance of a serious link.

Professor Alan Dunlop, who first suggested building a bridge over the Irish Sea, released drawings of what a crossing connecting the two countries could look like.

Prof Dunlop, who is one of the UK’s leading architects and a Fellow of the Royal Incorporation of Architects in Scotland, says the creation of a 25-mile tunnel or a bridge is entirely feasible, despite it being heavily criticised.

But he has told the Herald on Sunday he fears that the scheme is dead in the water because of the Prime Minister's hopes of building an "underground roundabout" as part of the plan.

READ MORE: 'Put the hallucinogenics down': Prospect of undersea tunnel between Scotland and Northern Ireland debunked

The idea would involve as many three tunnels heading out from England and Scotland with a roundabout beneath the Isle of Man in a bid to iron out post-Brexit issues across the UK.

HeraldScotland:

The proposal included three starting points: at Stranraer, Heysham, near Lancaster, and one near Liverpool. Then a single tunnel would run on from the Isle of Man to Northern Ireland.

Since the conclusion of the Brexit transition period on December 31, the crossing idea has been pushed into the spotlight, as the Northern Ireland protocol included in the Brexit withdrawal agreement sees the region remaining within EU trade regulations.

The bizarre new scheme has come amidst talks of an undersea tunnel between Scotland and Northern Ireland, named ‘Boris’s Burrow’.

Experts say the new scheme would involve 105 miles of tunnel between Belfast and Liverpool. All the tunnels would be somewhere between two and a half and six times longer than the current longest road tunnel in the world.

Norway's Lærdal Tunnel at 15.23 miles long, the longest road tunnel in the world and provides a ferry-free connection between Oslo and Bergen.

Chairman of Network Rail, Peter Hendy, is currently studying the route and is expected to publish his findings within weeks.

A proposed high-speed rail tunnel could be completed in five years, according to some.

Experts have questioned the bridge’s practicality, given the weather conditions in the Irish Sea and the position of Beaufort's Dyke trench, which contains dumped wartime munitions.

Prof Dunlop, visiting professor at Robert Gordon University's Scott Sutherland School of Architecture who has taught at schools of architecture internationally, now fears the worst for the plan.

"I believe Boris Johnson's proposal for a roundabout under the Isle of Man has finally put an end to a serious consideration of a road and rail tunnel linking Scotland and Ireland. The idea has been universally slammed as ridiculous," he said.

HeraldScotland:

"I can't think myself why Johnson would say that, particularly at a time when there is so much criticism being levelled at the PM and so called Boris's Burrow.   It only serves to undermine that which I know to be structurally, technically and physically achievable; that is a tunnel or bridge that connects Scotland with Ireland.

"The latest proposal for a roundabout below the Isle of Man is not credible. It undermines and puts at risk the probability of a serious feasibility/scoping study for a road and rail tunnel linking Scotland with Ireland."

READ MORE: Transport review to examine feasibility of building a bridge or tunnel between Northern Ireland and Scotland

If a tunnel was approved it would run under the Irish Sea between Portpatrick, in the south west of Scotland and Larne in Co Antrim. A potential route for a bridge is from near Campbeltown, Scotland to Northern Ireland’s Antrim coast.

Sir Peter Hendy has already met with Scottish secretary Alister Jack and Mr Johnson, who is said to be "very enthusiastic" about the proposal.

Mr Jack has previously told a Holyrood committee that he preferred the idea of a tunnel to a bridge, which would be estimated to cost around £20bn.

If approved, it is believed that the tunnel could cost some £10 billion to construct, and could be modelled on the Channel Tunnel linking Britain and France.

But the prospect has been met with disdain in some quarters.

Conservative MP Simon Hoare, chairman of the Northern Ireland Select Committee dismissed the idea of an undersea tunnel as fanciful and said the government's focus should be on making the protocol work.

"The trains could be pulled by an inexhaustible herd of Unicorns overseen by stern, officious dodos," he said.

"A PushmePullYou could be the senior guard and Puff the Magic Dragon the inspector. Let’s concentrate on making the protocol work and put the hallucinogenics down."

He later said there are several practical barriers in the way of the rail project.

"Also another 'minor hurdle' is the NI railway gauge is an 'all Ireland' gauge which is different to that used in GB," he said.

"I’m not Brunel but I think this might be a bit of a problem."

HeraldScotland: Michael Matheson in Holyrood

Scottish transport secretary Michael Matheson has also previously rubbished the idea of a fixed link between the nations as the Prime Minister's “vanity project”.

Mr Jack stated his belief that Mr Hendy will recommend the construction of a tunnel rather than the bridge originally proposed in 2018, saying: "My strong inclination would be that he thinks it should be a tunnel because he and I have had conversations about the weather patterns in the Irish Sea and Beaufort’s Dyke, and there’s a munitions deposit there."

Stormont’s minister for infrastructure Nichola Mallon has poured scorn on it describing it as a “Tory glamour project”.

But Prof Dunlop, who was awarded the Royal Gold Medal in Architecture from the Royal Scottish Academy debunked the debunkers and said there were simple solutions to the issues raised.

A variable gauge system, used in other trains that cross borders could be used.

As for Beaufort's Dyke, he said a tunnel would loop around it not over it.

"Both the tunnel and bridge are achievable, there are precedents," he said. "A floating tunnel which sits below the surface and is secured to the sea bed as in Norway and does not have to be buried underground, which is the mistake many are making (Boris's Burrow) would cost less than a bridge, by my calculations but you lose the iconography and symbolism that comes with a bridge.

"Even the Queensferry crossing is symbolic of a forward looking country. It is hard to get worked up about a tunnel.

HeraldScotland:

"Look at the Millau Viaduct bridge which spans the Tarn Valley in Southern France, and wonder. It's known worldwide, what ambition, that's what a country can achieve. A tunnel, not so much."

One of the advantages of a tunnel include the lack of impediment to shipping during construction or operation, increased security from weather and terrorism, and lower maintenance.

"The current thinking is a tunnel not a bridge as I first researched," said Prof Dunlop.

"The tunnel breaks through and emerges at Port Mora and Laird's Bay, two miles north of Portpatrick. That area of the Galloway coastline is defined by high sand stone sea cliffs which run into the sea to form a ledge below the wave live, before dropping where the sea gets much deeper. I think at this point a terminal can be constructed. That's what my drawings indicate.

"It's an architectural piece, but the terminal is intended to suggest that it rises from the ledge and is sensitive to the landscape, context and sea front setting.

"The tunnel loops to the north of Beaufort's Dyke beyond the known munitions dump and continues down from that point to a level of 12 metres below the wave line, so ship can pass over. Pontoons, harnessed to the sea bed by cable ties, are set at 200 metres centres and support the tunnel below, with sea lanes openings of a greater width of 400 metres set at intervals. Pontoons are designed to capture wave energy.

"There are many cross border countries that have different train gauges, Spain and France for example. Variable gauge adjustable wheel sets here are adopted. The same would be achievable between Ireland, Scotland and the UK."

He believes a crossing makes sense in terms of cost to those using it. He believed hauliers can pay, as much as £600 per return journey by ferry and he said one operator makes 20 crossings for each week of the year. Passengers pay £300 for a return.

"That soon stacks up," he said.

"I set the initial cost of £20bn for a bridge. My estimate was calculated from the cost of ten equally complex structures from all over the world, from Prince Edward Island, Hong Kong and Macao, the Norwegian Coastal Highway to the Millau Viaduct.

"A tunnel would not be as expensive as the geological challenges would not be so great, but as I say I'm no economist."