The tunnel extends beneath the English Channel at the Strait of Dover. It is the only fixed link between the island of Great Britain and the European mainland. It allows the city of London to be directly connected by train to Paris, Lille, Brussels, Amsterdam and Cologne – thanks to the Eurostar and Thalys train lines.

The Channel Tunnel (or "Chunnel") offers three massive advantages over air or ferry travel: speed, reliability, and environmental impact. The Eurostar train connects London to Paris in just 2 hours and 16 minutes, significantly faster than flying when you factor in travel to airports, security lines, and baggage claim. Unlike ferries, the tunnel is unaffected by the frequent storms and high winds of the English Channel, meaning it rarely suffers from weather-related cancellations. From a cargo perspective, the Eurotunnel Le Shuttle allows trucks to cross in just 35 minutes, keeping the UK's supply chain moving 24/7. Environmentally, a train journey through the tunnel emits roughly 90% less CO2 than an equivalent short-haul flight. In 2026, as carbon taxes on aviation rise, the tunnel has become the primary choice for "green" business travel between the UK and mainland Europe, further bolstered by the direct rail links now reaching as far as Amsterdam and Cologne.