Saudi Aramco, the world’s largest oil company, is being readied for market. At the moment it is owned entirely by the Saudi Arabian government, but next year, if all goes to plan, anyone in the rest of the world will be able to buy a share in it.

The numbers are huge. Aramco pumps 12 per cent of the world’s oil supplies, five times as much as the largest non-state owned oil company, ExxonMobil. It sits on the world’s largest oil reserves. Potentially it will become the world’s most valuable company, with some people suggesting that it will be worth five times that of Apple. Even if only 5 per cent of the company is floated initially, as is the plan, that will still make the offer the largest that the world has ever seen. It will be the world’s largest privatisation by far. And so on.

Anything of this size is going to change, if not the world, at least the country, the region and the energy industry. So what might it mean?

There are at least three stories here. One is Saudi Arabia’s need to reduce dependence on oil, and to use its oil wealth to finance diversification. A second is the impact of this on global finance. And a third, going beyond economics, is the effect on the Middle East more generally.

The Saudi problem is a familiar one, where dependence on a single industry crowds out other activities. It has been dubbed the Dutch Disease, because when North Sea gas was first developed by the Netherlands, it pushed up wages and other costs and made the rest of the economy uncompetitive. The Netherlands coped because it had a strong civic society and, in any case, the energy industry never dominated to the extent that it does in Saudi Arabia or indeed Russia. To counter this the Saudi Deputy Crown Prince, Muhammed bin Salman, announced the Vision 2030 plan, which involves raising money by selling part of Aramco to fund other industries and to build up what it aims to become the world’s largest sovereign wealth fund. Thus, part of the money is reinvested in the country and part invested abroad.

The intention is admirable, and if the recent plunge in the oil price says anything it is that it is too dangerous to rely on a single industry. Critics have noted that this is very much a government-driven top-down project rather than a market-driven bottom-up one, but it is hard to see quite how the country can do anything other than this to get the economy to diversify. Prince Salman, who is 30 and a leader of the next generation of the ruling royal family, suggests investment in tourism, health care, manufacturing, and education. One aim is to increase the private sector’s share of the economy from 40 per cent to 65 per cent. If this happens, Saudi Arabia will become more “normal”, more like the diversified economies of, for example, Oman. That will inevitably change the character of the nation too.

The second issue, the impact on global finance, falls into two parts: the sale itself, and the build up of the sovereign wealth fund. As far as the sale is concerned this will be a test as to how much investors want to put into a mature industry. There is of course a huge debate as to the speed at which the world economy can get away from fossil fuels. But oil and gas are less threatened than coal – they are somewhat cleaner for a start. So we will see to what extent investors will put money into this industry, given the additional factor of political risk on top of environmental risk.

As for the sovereign wealth fund, well, it exists already, and this clutch of investors has already shaken up world markets. Sovereign funds can take a long-term view that most investment vehicles can’t. They can also take moral stands: Norway is divesting of its holdings in the coal industry on environmental grounds. Saudi Arabia has already considerable power as an investor. If all goes to plan that power will become much greater. We have become used in Britain to have much of our investment, particularly in property, to be financed by foreigners. That balance will shift even further.

Finally there is the impact on the region. If the Saudi economy becomes more broadly-based, more “normal”, then that will affect its neighbours. At a practical level, if this proves an effective way to raise funds, expect other governments controlling national oil companies to sell off some of those shares too. This will mean greater scrutiny of their activities, because if you sell shares to global investors you have to comply with international accounting and legal standards. What happens at Aramco will become a modernising force for the region. Is the unequivocally positive? Well, probably, yes.

There is a final twist to this tale. The world’s largest privatisation will cap what must be Britain’s largest intellectual export over the past 50 years, the big idea developed in the UK that has been imitated around the world. The first big share sale was that of British Petroleum, begun in 1976 by Denis Healey, the Labour Chancellor. The precursor of BP was the Anglo-Persian Oil Company, based in Iran just across the Gulf from the precursor of Aramco, an offshoot of Standard Oil group, now ExxonMobil. So the first major privatisation was of an oil company that struck oil on one side of the Gulf, and the biggest one will be of an oil company that stuck oil on the other.