Digging an eight mile, $3bn (£1.6bn) tunnel linking Europe to Asia beneath the Bosphorus, a few miles from one of the world’s most active seismic faults, was never going to be easy. But in 2005, a year after the project started, engineers working for the Turkish authorities were surprised by a discovery: the remains of the 4th century port of Constantinople, hailed as the greatest nautical find in a century.

Archaeologists were understandably thrilled. Yet the engineers were frustrated by the delays, which at their worst cost $1m a day. The project is still two years behind schedule.