Short answers, pulled from the story.
French mining engineer Albert Mathieu-Favier sketched a plan for an undersea tunnel in 1802. His design featured oil lamps for illumination and horse-drawn coaches moving through bored tunnels.
Tunnelling work began in 1988 using eleven specialized boring machines designed through joint ventures between American, British, and Japanese manufacturers. The service tunnel broke through first on the 30th of October 1990 creating a pilot passage ahead of main lines.
Actual costs reached £4.65 billion at completion representing an 80% overrun compared to initial estimates. Financing costs proved 140% higher than forecast due to delays and enhanced safety requirements.
Ten workers died between 1987 and 1993 mostly within early boring phases. Daily expenditure exceeded £3 million at peak construction levels employing up to 15,000 people across both sides.
Official opening occurred one year behind schedule on the 6th of May 1994 during ceremonies attended by Queen Elizabeth II and President François Mitterrand. Full public service started months later after phased approvals from safety authorities.