Standing in the centre of Soho Square Gardens, admiring what was once one of London’s most fashionable areas, you will likely be totally oblivious to what is happening underneath your feet. Twenty-four metres below street level, running under countless listed townhouses, the trains of the new Elizabeth line are hurtling, almost silently, at speeds of around 60 mph – revolutionising rail travel in the capital, and cutting commute times for those living outside London.