Boris Johnson has been advised in an official report that his plan for a bridge or tunnel from Scotland to Northern Ireland would cost up to £330bn — over 20 times more than originally thought — and would be “impossible to justify”.
The UK prime minister a year ago commissioned Sir Peter Hendy, the chair of Network Rail, to examine the feasibility of a new transport link across the Irish Sea. But his report, published on Friday morning, concluded that the project was a non-starter, saying: “The benefits could not possibly outweigh the costs to the public purse.”
Johnson had seen the idea of a link across a 21-mile stretch of the Irish Sea as a way to strengthen ties between different parts of the UK, partly because of the upheaval caused by his own hard Brexit.
But the idea was memorably described by Dominic Cummings, former chief adviser to Johnson, as “the world’s most stupid tunnel”.
Hendy said his “in-depth, evidence-based assessment” had concluded that either scheme would be possible to build. But a bridge would cost about £335bn and a tunnel would cost up to £209bn, with either project taking about 30 years to build.
The estimate for a bridge is 22 times higher than Johnson’s 2019 costing of “about £15bn”. It comes after the government last week announced it was scrapping part of the eastern leg of the High Speed 2 rail line to Leeds and downgrading the HS3 route from Leeds to Manchester to try to save tens of billions of pounds.
The proposed bridge would have crossed Beaufort’s Dyke, a sea trench more than 1,000ft deep in places, requiring huge support towers. The area — which is wracked by gales — was also used as an offshore ammunition dump during the second world war.
Hendy said the government should not progress the idea any further, saying: “Whilst the economic and social effects would be transformational, the costs would be impossible to justify, given the government’s already very significant commitment to long term transport infrastructure improvement for levelling up.”
However, he added that the investigation into the feasibility of the link “was an excellent question to ask” given that politicians and engineers had argued about the wisdom of a Scotland-Northern Ireland crossing without any evidence base.
The report was published alongside Hendy’s separate Union Connectivity Review, which called for a package of railway and road improvements to improve transport in the regions.
One of its key recommendations was the creation of a strategic transport network across the UK, much like the US Federal Transit Authority, to shore up the union.
Called UKNet, the new body would work with the devolved administrations to develop local connections and provide extra funding for underperforming areas of the rail network.
The review called for an overhaul of subsidy rules for domestic aviation to allow support for routes between different regions of the UK (rather than just to and from London) and to allow multiple airlines to serve a single route.
Hendy also recommended more investment in the West Coast main line north of Crewe; upgrading the A75 to improve road links with Northern Ireland; relieving congestion on the M4; and improving connectivity between north Wales and north-west England on the A55, M53 and M56 roads.