While laying brick on top of another or connecting metal poles together into a tall structure might seem like a manageable task if one puts enough effort, digging a tunnel underneath a large body of water seems like a task of a completely different caliber. But that didn't scare some people and all the way back to the 19th century, proportions were put forth, like that of a French mining engineer Albert Mathieu-Favier, who introduced the idea of digging a tunnel under the English Channel. Though despite many efforts from different persons and groups, only in 1979 did the concept start to gain speed when the British prime minister Margaret Thatcher supported the idea of a privately funded project. Two years later, Thatcher and the French president François Mitterrand agreed to work together on a privately funded proposal. With many agreements, funding schemes and years of work from both countries, the construction began in 1988. Eleven tunnel boring machines were used to cut through chalk marl to construct two rail tunnels and a service tunnel. The construction took £4.65 billion (equivalent to £13 billion in 2015), around 15,000 people and claimed 10 workers' lives. The tunnel is 50.45 km (31.35 mi) long and began operating in 1994 after it was formally opened by Queen Elizabeth II and President Mitterrand in May.