Not long after he took over as chief executive of Tesco, I had dinner with Phil Clarke.

At that moment he was king, master of the dominant force in UK retailing, head of a company that, while it had suffered a blip in California, was on a seemingly relentlessly upward track. But far from exuding triumphalism, he was genuinely worried.

What was bothering him, he said, was Amazon. The US online titan had just begun testing fresh produce deliveries in its home patch of Seattle. It already sold non-perishables. So, said Clarke, it was only a question of when, not if, it decided to take the plunge and go for groceries. And, having seen the havoc wreaked by Amazon elsewhere on the high street, he was understandably nervous.

It was clear that his was no idle fear. The boss of Tesco is surrounded by myriad advisors, analysts and forecasters. He, or they, had seen something – a chart, a spreadsheet – that had provoked alarm.

Come forward some years, to today. Clarke has gone, and his successor Dave Lewis, is entitled to be feeling chuffed. He had a tough baptism, but now Tesco is to merge with Booker, the UK’s largest wholesaler, in a £3.7bn deal, and the regulator, the Competition and Markets Authority (CMA), has given it unconditional provisional approval.

That may change, of course. The CMA’s final decision is due very soon, possibly next week, but having signalled its intent, for the watchdog to change course or to impose onerous remedies this late in the day would be very strange indeed.

It’s possible that the CMA may order Tesco to dispose of some of its convenience stores, but even if that happened, the pain would not be too difficult to bear – McColls, for one, is on record as a willing buyer. Tesco would still have its eye on the bigger picture, of capturing Booker, and the synergies and buying power that would bring, plus the recruitment to the board of the wholesaler’s highly regarded chief, Charles Wilson.

The CMA’s effective green light has rightly caused shock in the industry. Leading retail analyst, Clive Black of Shore Capital, draws the comparison with the “CMA’s singular derailing” of the 2015 marriage of Poundland and 99p Stores. Calling it the “Comedy Markets Authority”, he says: “We imagine that there will be understandable consternation and no little shortage of apoplexy with the hard-to-predict Competition regulator.”

Ex-Asda boss, Andy Clarke, said: “I think we were all surprised by the first phase ruling … I think we all expected [the CMA] to have a number of requests. For it to get a clean bill of health was quite surprising.”

Comparisons have been made, not only with Poundland and 99p Stores, but with Asda’s 2010 acquisition of Netto, and Morrisons’ 2004 purchase of Safeway – which were heavily challenged by the CMA.

While the reaction to the go-ahead has focused on the immediate ramifications for Tesco, and much praise has been heaped upon Lewis and his cohorts for achieving their desired victory, it’s worth pausing, to look at what the decision implies. For it would appear that the CMA is also concentrating on the bigger picture.

That has to be the only explanation for the regulator’s move. And from where Tesco is sitting, the reasoning does not make for necessarily pretty viewing.

The CMA is effectively saying that where UK grocers are concerned, anything goes – that the internet has altered the landscape for good, in a way that no one ever thought likely. According to Black: “What this decision may mean is further material change to the make-up of the UK wholesale market; who will benefit from this? Who will lose? More broadly, unconditional clearance raises the question of what cannot possibly merge in the wider UK food market.”

Previously, it was always thought that the consumer was best served by having four national players. With the Tesco-Booker ruling, that is no longer so.

Business news: In pictures Show all 13 1 /13 Business news: In pictures Business news: In pictures Flybe collapses Airline Flybe has collapsed. All future flights on the Exeter-based airline have been cancelled – leaving more than 2,300 staff facing an uncertain future, and wrecking the travel plans of hundreds of thousands of passengers. The chief executive, Mark Anderson, said: “Europe’s largest independent regional airline has been unable to overcome significant funding challenges to its business. AFP via Getty Business news: In pictures Future product placement will be 'tailored to individual viewers' Marketing executives say that product placement in films and televison shows on streaming services such as Netflix may be tailored to individuals in future. For instance, if data shows that a viewer is a fan of pepsi, a billboard in the background of a shot would host an advert for pepsi, while for a viewer known to have different tastes it could be for Coca-Cola Paramount Business news: In pictures Corbyn wishes Amazon a happy birthday In a card sent to Amazon CEO Jeff Bezos on the company's 25th birthday, Labour leader Jeremy Corbyn writes: "You owe the British people millions in taxes that pay for the public services that we all rely on. Please pay your fair share" Business news: In pictures No deal, no tariffs The government has announced that it would slash almost all tariffs in the event of a no-deal Brexit. Notable exceptions include cars and meat, which will see tariffs in place to protect British farmers Getty Business news: In pictures Fingerprint payment NatWest is trialling a new bank card that will allow people to touch their hand to the card when paying rather than typing in a PIN number. The card will work by recognising the user's fingerprint NatWest/PA Wire Business news: In pictures Mahabis bust High-end slipper retailer Mahabis has gone into administration. 2 Jan 2019 Mahabis Business news: In pictures Costa Cola Coca-Cola has paid £3.9bn for Costa Coffee. A cafe chain is a new venture for the global soft drinks giant PA Business news: In pictures RIP Payday Loans A funeral procession for payday loans was held in London on September 2. The future of pay day lenders is in doubt after Wonga, Britain's biggest, went into administration on August 30 PA Business news: In pictures Musk irks investors and directors Elon Musk has concluded that Tesla will remain public. Investors and company directors were angry at Musk for tweeting unexpectedly that he was considering taking Tesla private and share prices had taken a tumble in the following weeks Getty Business news: In pictures Jaguar warning Iconic British car maker Jaguar Land Rover warned on July 5, 2018 that a "bad" Brexit deal could jeopardise planned investment of more than $100 billion, upping corporate pressure as the government heads into crucial talks AFP/Getty Business news: In pictures Spotif-IPO Spotify traded publically for the first time on the New York Stock Exchange on Tuesday. However, the company isn't issuing shares, but rather, shares held by Spotify's private investors will be sold AFP/Getty Business news: In pictures French blue passports The deadline to award a contract to make blue British passports after Brexit has been extended by two weeks following a request by bidder De La Rue. The move comes after anger at the announcement British passports would be produced by Franco-Dutch firm Gemalto when De La Rue’s contract ends in July. The British firm said Gemalto was chosen only because it undercut the competition, but the UK company also admitted that it was not the cheapest choice in the tendering process. Business news: In pictures Beast from the east economic impact The Beast from the East wiped £4m off of Flybe’s revenues due to flight cancellations, airport closures and delays, according to the budget airline’s estimates. Flybe said it cancelled 994 flights in the three months to 31 March, compared to 372 in the same period last year.

Former Asda chief, Clarke, said: “I’m sure there are many discussions going on around the country about whether four becomes three, because what the CMA have sort of said is: ‘It’s open season.’ Whether that’s the reality or not, I don’t know, but it makes you think that could be the case.

“The combined shares of any of the other three, as a twosome, would be less than Tesco and Booker. Who would have ever thought that would be the case?”

What this means is that we’re heading for a shake-up in the supermarket sector. The small but strategically important Booths is already up for sale. But, in the year ahead, expect more dramatic shifts.

The CMA is now unlikely to stand in the way of a long-mooted Sainsbury and Morrisons union. Or Sainsbury and Marks & Spencer.

More radical still, however, would be the arrival of Amazon. When Phil Clarke shared his dread of Amazon, that was when the online giant had just dipped a toe in the water by commencing grocery deliveries.

Heaven knows what he would be saying after Amazon’s swoop a few months ago on Whole Food Markets in the US.

Amazon has realised it requires bricks and mortar outlets if it’s going to achieve its aim in food. At present, it has nothing in the UK to help in the fulfilment of that plan.

Suddenly, thanks to the CMA, those nerves about Amazon look extremely justified. If I were Lewis at Tesco, pleased at scoring a coup with Booker, I’d be keeping my celebrations very much in check.