Irish-GB Bridge?

From the BBC:
"A bridge across the Irish Sea and four other amazing plans"

A tunnel or bridge between Britain and Ireland has been discussed for decades. It would boost tourism and business activity on both sides of the Irish Sea, supporters argue. But what about the engineering? Bridges are normally cheaper. But a UK-Ireland bridge would have to be long. Donghai Bridge at 20.2 miles linking Shanghai and offshore Yangshan is sometimes called the longest sea bridge. In the most realistic locations, a bridge to Northern Ireland or the Republic would be even longer. A 21-mile bridge from Galloway in Scotland to Northern Ireland was proposed in 2007. Think-tank the Centre for Cross Border Studies put forward the proposal to provide international rail links that could compete with air services.  The Chambers of Commerce of Ireland called in 2005 for a part tunnel, part bridge link to carry trains between Tuskar, County Wexford, in Ireland and Pembrokeshire in Wales. Three-quarters of Irish firms surveyed at the time said that a fixed link with Europe was vital. The Irish Academy of Engineers has envisaged a 50-mile rail tunnel with a journey time from Dublin to Pembrokeshire of 70 minutes.  Four main routes have been proposed. Two run from Scotland to Northern Ireland - Campbeltown to County Antrim, or Stranraer to Belfast. Two run from Wales to the Republic, a northern and southern route, where the Welsh peninsula juts into the Irish Sea.  Bill Grose, former chairman of the British Tunnelling Society, says there are two critical issues for siting the tunnel. First, the location that most supports transport demand, and how well served that location is by rail and road links. Second, the shortest distance across the sea.  Holyhead to Dublin is about 50 miles of water, Fishguard to Waterford is about 45 miles and Stranraer to Belfast is about 20 miles.  The Campbeltown to County Antrim route is only 12 miles but the town is in an isolated part of Scotland that would need transport links to be cut through mountainous terrain.

The most financially viable appear to be those from Wales to the Republic, Grose says. "Intuitively Holyhead to Dublin is a more preferable route than the others. It's closer to Manchester and Liverpool and connects straight into Dublin."  Rail rather than road would be more realistic both financially and from an engineering point of view, he says. Rail tunnels cost about £60m a kilometre (accounting for one tunnel in each direction).  Road tunnels need to be about 50% bigger and a tunnel between Holyhead and Dublin would need a ventilation island halfway, which would not be cheap. With the Channel Tunnel historically struggling to make money on a much bigger catchment area - the UK and continental Europe - many will doubt whether there is really the business case for the tunnel.

Also the benefits would be much greater in Ireland, which would gain a through-route to continental Europe, than in Britain, which would only gain a route to Ireland. The Irish government would be called on to provide at least half the cost, something that might seem unlikely in these straitened times. Cost: Bridge at £3.5bn (2007 estimate by Centre for Cross Border Studies), tunnel much more

^ This article had other proposed projects, but I wanted to focus only on the idea of a bridge or tunnel from Ireland to Great Britain (technically you can't say the UK since that includes Northern Ireland and that shares a land border with Ireland.) I don't see a bridge or tunnel being built from Scotland to Northern Ireland (with all the fighting and violence that still continues there despite a 1998 Peace Treaty.) A link between Wales and Ireland is more feasible (at least more securely.) The British and French built the Chunnel under the English Channel and yet you always hear the trains have constant problems and are shut-down due to fires, flooding, etc so who knows if the same would happen here. ^

http://www.bbc.co.uk/news/magazine-23672538