Tunnelling expert Bill Grose has extensively discussed the potential benefits of constructing a tunnel connecting Wales to Ireland, which he believes could be a more attractive option compared to the previously suggested link between Scotland and Northern Ireland. Grose, a highly regarded figure in the field and former chair of the British Tunnelling Society emphasised that the existing infrastructure in Holyhead and Dublin makes the Wales-Ireland route particularly appealing to investors when compared to the Belfast-Stranraer link. He pointed out that Dublin is a considerably larger city than Belfast, and Holyhead boasts more developed infrastructure than Stranraer, significantly reducing the associated business risk. Grose highlighted the advantageous proximity of major cities like Liverpool and Manchester to Holyhead, along with the existing road and rail networks in place, making the Wales-Ireland connection a more practical and feasible option from a transportation perspective.
Another favourable factor that Grose cited in favour of the Wales-Ireland tunnel is the relatively shallow water depth in the Irish Sea between Dublin and Holyhead, with its deepest point reaching 120 meters. This manageable water depth opens up the possibility of constructing an island, platform, or cofferdam at a midpoint in the sea, which could serve as a ventilation or access point for the tunnel. This favourable condition significantly enhances the attractiveness of the tunnelling project in terms of its engineering feasibility.
Regarding the financial aspects, Grose estimated that the tunnelling costs for the Wales-Ireland project would likely fall within the range of £5 billion to £7.5 billion, with a total project cost of approximately £15 billion as a reasonable initial estimate. The exact nature of the proposed tunnel, whether it would primarily accommodate road or rail traffic, remains uncertain, Grose expressed his endorsement of rail as a more realistic and viable option. He highlighted the advanced technology and expertise available for long-distance rail tunnel travel, making it a more developed and reliable mode of transportation compared to road tunnels. Notably, the proposed Wales-Ireland tunnel would be near twice the length of the 50km Channel Tunnel, making it a substantial engineering endeavour.
Following the initial suggestion of a bridge, various alternatives have been proposed for a Scotland-Northern Ireland crossing. Recently, Downing Street officials put forward a concept involving three separate tunnels under the Irish Sea, which would converge in an "underground roundabout" beneath the Isle of Man. The three starting points for these tunnels would be Stranraer, Heysham near Lancaster, and a location near Liverpool. From the Isle of Man, a single tunnel would continue the connection to Northern Ireland.
Grose, having previously highlighted the challenges associated with the Scotland-Northern Ireland proposal, drew attention to the Wales-Ireland suggestion's advantage in terms of total tunnelling distance. He explained that the distance from Holyhead to Dublin is similar to that of Liverpool to the Isle of Man. However, building a tunnel from Holyhead to Dublin would provide a direct connection to the island of Ireland, whereas reaching the Isle of Man would only be halfway towards the ultimate destination.
Formal proposals for an Irish Sea link between Scotland and Northern Ireland have been submitted as part of the government's ongoing Union Connectivity Review. This comprehensive review aims to enhance transport infrastructure across Scotland, Wales, Northern Ireland, and England, encompassing road, rail, air, and sea connections. Scheduled to be published in the summer, the final report will shed light on the potential for a "fixed link" across the Irish Sea. In the interim report, the need for further exploration of such a link has already been identified, indicating the seriousness with which the proposal is being considered.