Mergers and acquisitions bankers who specialise in the oil and gas sector are among the small number of those who, over the past five years, have been able to claim to have been consistently busy without an eyebrow being raised.

However, the conditions in which their clients operate have been anything but steady, as new technology, new demand and new supply - most noticeably the masses of shale gas discovered in the US - have shaken up the entire industry.