As oil prices began to tumble last year, bankers watched from the sidelines eagerly hoping that there would be a revival of the blockbuster oil and gas deals that created the world's biggest players almost two decades ago.
At first, the oil rout meant that some smaller deals unwound, such as Dragon Oil's proposed pounds 500m takeover of Petroceltic. Then there was a string of announcements from oil majors pulling out of expensive exploration projects in the North Sea, which were not viable in the new environment.
For the most part, companies appeared to be in "watch and wait" mode. Despite expectations that there would be consolidation in the industry, the see-sawing of the oil price makes structuring any deal difficult. Potential buyers refuse to overpay in case they are left red-faced if the oil price continues to tumble, while sellers are wary of giving in to a bargain-basement price.
Royal Dutch Shell stayed out of the consolidation in the late 1990s. However, this time, rather than waiting for someone else to dip their toe back into dealmaking, the company has created an almighty pounds 47bn splash and the ripples are expected to be felt for the next year.
"Shell missed out on the late 1990s mega-merger wave due to its complex shareholding structure of being 60pc Dutch and 40pc British," said Christian Stadler of Warwick Business School. "Mobil for example would have been a perfect fit but ended up in the arms of Exxon because of this. This time round Shell has no such issue, being a normal UK plc."
The deal started to become a reality on the afternoon of Sunday March 15, when Ben van Beurden, Shell's chief executive, felt the time was right to make a "bold move" and pick up the phone to BG chairman Andrew Gould.
"It was very simple. I called Andrew up to see if it was possible to have a constructive discussion about the idea and it very quickly seemed to make sense to both of us," van Beurden said.
The deal was engineered in a little less than four weeks by a small team of advisers. However, the talks reached a pressure point over how much Shell should be paying for an asset which lost 30pc of its value over the past year. "We all worked very well during the period, but there were moments of course when talking about valuation," van Beurden said.
None the less, Shell's readiness to pay 50pc more than BG's share price is expected to give other potential buyers more confidence and justification for paying up in their prospective deals.
"This deal is fantastic for sentiment," said Neil Passmore chief executive at Hannam & Partners, the advisory outfit set up by former JP Morgan mining banker Ian Hannam. "The premium sets an instant marker for all those other bid discussions to be judged against."
With BG now tied up with Shell, the next in line for a deal looks to be Tullow Oil, followed by rival London-listed players Genel, Nostrum Oil and Gas, Ophir and Cairn Energy.
Augustin Eden, analyst at Accendo Markets, said: "In the past last year BG shares fell by 30pc, shares in Tullow Oil have fallen 65pc and Premier Oil is down 55pc, meanwhile sector behemoths BP and Royal Dutch Shell have only shed 10pc over the same period, leaving them in the position of predator rather than prey. This could mark the beginning of an M&A rave."
Despite BG's problems, which include issuing four profit warnings in 18 months leading up to January last year, there is another factor behind Shell's offer of such a hefty premium for the company. It also acts as a knockout blow and make it difficult for another rival buyer to compete.
ExxonMobil has been regularly linked to BG and now faces a serious challenge from Shell both in size and production capabilities in liquefied gas and oil. A combined Shell and BG can produce 4.2m barrels of oil - putting it ahead of Exxon's output of around 4m last year.
Exxon has a triple-A credit rating, greater financial firepower and the possibility of tax advantages, provided it could navigate America's tightened inversion rules, meaning there is still a risk it could gatecrash the deal by offering investors a bigger cash portion.
However, Shell is likely to sell its deal to BG investors with the idea of them owning 19pc of the new company, which will allow them to benefit from the upside in oil recovery and higher payouts.
In addition, hostile deals for British companies are notoriously tricky and a three-way contested fight almost fantasy talk due to UK takeover panel restrictions that tie any potential bidder to a strict four week timeline.
As BG's Gould said: "Until the deal closes we have an obligation to consider any serious competing offer. But frankly at this point of time we think that this is the best combination."
Both sides have to sell the blockbuster deal to shareholders and Shell will face some concern that the deal will stretch its balance sheet.
But amongst institutional investors there is a huge appetite for growth in this environment of low interest rates and a falling oil price, and the quickest way to boost earnings is by buying them.