The incredible £208bn tunnel from Britain to Ireland that would be 54 miles long

This incredible project, estimated to cost around £208 billion and span 54 miles between and , is just one of a number of projects proposed to link the two countries together – one that would be “six times the length” of any other tunnel created.

Known as the ‘Irish Mail route’, the £200bn version of the scheme was considered and ultimately rejected by the UK government in 2021 – with the Financial Times reporting that it was “dead, at least for now” in September of that year.

A document released at the time stated that chair of Network Rail Sir Peter Hendy had “agreed to add a seventh corridor … between Holyhead and Dublin”, but balked at the “environmental and scale concerns” of the plans.

It doesn’t mean the tunnel is completely off the table, though. A link between the two countries had been proposed as long ago as Victorian times before again rearing its head in the 1960s and under ’s premiership five years ago, when the then-PM suggested a bridge be built between and Ireland.

And as well as acknowledging its detractions, the 2021 report suggested that the project would create over 35,000 new jobs and deliver a major boost to the UK economy. It also hinted at the structure’s generation of “renewable energy from wind, tidal and solar sources”, earning it the badge of a sustainable and large-scale infrastructure project if resurrected down the line.

Travelling between Ireland and Wales currently takes upwards of four hours, with various airplane and ferry options available. Whereas the tunnel route would be estimated to take around 30 minutes by car.

The Irish Mail route – while bearing a hefty price tag and taking up to 30 years to build – is also a frontrunner model because of its cohesion with existing road and rail routes in both Dublin and Holyhead.

It was first laid out by the British Transport Research Centre in 2014, with researchers enthusiastic about its potential boost to tourism and business on both sides of the Irish Sea.

While alternatives, including between Ireland and parts of Scotland, were also considered, the Ireland-Wales route was judged to be the most viable.

“Intuitively, Holyhead to Dublin is a more preferable route to the others,” Bill Grose, former chairman of the British Tunnelling Society, told the .

“It’s closer to Manchester and Liverpool and connects straight to Dublin.”

Other potential tunnels include the Kintyre Route, connecting Rubha Chlachan in Argyll, Scotland with Antrim in Ireland – the shortest possible route but lacking in existing infrastructure links – and the Macassey Route, connecting Dumfries and Galloway with Whitehead in Antrim, which was the journey suggested by in his bridge proposal of 2019.

A tunnel seems more likely than its overground equivalent however. The 2021 government report estimated that a road and rail bridge would cost up to £335 billion and be “the longest span bridge built to date” – making it potentially even less feasible than the highly theoretical tunnel project.