Considering the height restrictions zoned into London’s super-prime real estate, the only practical way for some owners to expand is to go underground (as deep as five stories’ worth of “basement”), which requires heavy digging machines. However, by the time the excavation is finished, the machines are mired at the bottom of a huge pit with no easy way to bring the behemoths up. Consequently, on some jobs, reported the New Statesman in June, property owners have elected merely to leave the machines buried under what would be their sub-basement.