Using rail links to turn clusters of cities into single metropolitan units is becoming a bit of a habit for European governments. There’s one plan to use a high speed rail link across the Pennines to merge the cities of England’s north. There’s another to connect Sweden’s second city, Malmo, to the Copenhagen metro.

Now, it turns out, there’s a plan to do something similar further east. (Honestly, the sea bed beneath the Baltic is going to look like Swiss cheese.) Earlier this year authorities in the Finnish capital, Helsinki, and the Estonian one, Tallinn, announced that they were looking into the possibility of linking the two cities via an undersea tunnel.

If it goes ahead – a pretty big if – the project would cost €9bn at current prices, and, at a minimum of 50km from coast to coast, would be the longest undersea tunnel in the world. By way of comparison, the submarine portion of the Channel Tunnel between England and France clocks in at just 38km.

The project goes by the marvelous compound noun “Talsinkifix”, which might just be the single best word ever invented.

The plan, it should be stressed, isn’t going to happen any time soon. In April, the two cities, Herju county (which contains Tallinn), and the European Union (which has stumped up much of the money so far) announced they were tendering a €100,000 contract to conduct a feasibility study. Earlier this month that contract went to Estonian engineering firm Vealeidja, and a pair of consultancies, Estonia’s Finantsakadeemia and Sweden’s Sweco (which, as it happens, is working on the Copenhagen/Malmo project, too). This consortium is now looking into the relative costs and challenges of a tunnel, or some kind of tunnel/bridge combo. Its report should be ready in February.

But all this work is just to see if it’s worth drawing up more detailed plans: in other words, it’s a study into whether it’s worth conducting another study. What’s more, while the Estonian authorities have started including the plan in all their long-term strategy documents, their Finnish partners have made no such commitment.

There seem to be two reasons for this relative lack of enthusiasm. One is economics: the Finns are already rich, and so have less to gain from the link. The other is politics. Part of the rationale for such a project would be to provide a fixed link between the two cities that doesn’t involve travelling via Russia. Estonia – smaller, newer, and ruled from Moscow within living memory – is presumably more nervous about its giant neighbour to the east.

Map of Rail Baltica, including the Talsinkifix tunnel. Image: Wikimedia Commons.

If Talsinkifix (god I love that word) does happen, it would likely connect Helsinki to the Rail Baltica network, a proposed high speed line running from Berlin to Warsaw and the Baltic capitals. This would provide an alternative to the two existing lines, one of which runs through the Russian enclave of Kaliningrad, the other through Russian ally Belarus. Honestly, it’s enough to give a struggling oil-rich empire some kind of insecurity complex.