Oil is Britain’s thin red line against a hard Brexit. The North Sea provided an economic buffer during the “winter of discontent” of 1978 and the “Black Monday” stock market crash, which almost destroyed the City a decade later. It may have to serve the same defensive purpose again if Theresa May, the Prime Minister, bungles a deal to leave Europe, or even worse, fails to reach an agreement.

Often derided as an insignificant and declining industry by some economists, oil remains one of the country’s most reliable money spinners and sources of hard foreign currency export revenues. Think of what the UK would be like without the vast wealth generated by the equivalent of 44bn barrels of oil pumped from British territory over the last 40 years. The North Sea also makes Britain entirely unique within the European Union, which is otherwise mostly barren of “black gold”.

Without the near 1.7m barrels per day of oil equivalent – a measure including gas and other liquids – pumped from the UK continental shelf, the 27 nation bloc is entirely dependent on producers outside of its control such as Russia and Saudi Arabia. Of course, Norway, which sits outside the EU but still enjoys trade access, remains a trusted oil and gas ally for Brussels. Nevertheless, Britain’s exit will to a certain extent weaken the European project in terms of the world’s most valuable traded energy commodity.

Central to the role oil can play in protecting the economy and the pound from the shock of a hard Brexit is the Forties crude blend and the closely linked dated Brent price benchmark, perhaps Britain’s most instantly recognisable and globally significant brand quoted in financial centres around the world.

Dated Brent is used to price around two thirds of the world’s supply of 100m barrels every day. Assuming a price of $70 per barrel, that’s over $4.5bn of transactions daily. The benchmark, assessed by S&P Global Platts in London, dates back to the heyday of North Sea production in the Eighties when the once prolific Brent oilfield was among the world’s most productive reservoirs outside of the Opec club of predominantly Middle Eastern petrodollar states.

Although the last of the Brent platforms, floating 115 miles off the coast of Shetland, is being shut down, the so called “Brent complex” and price benchmark continue to thrive and evolve along with the demands of the global oil industry. As Brent itself has physically dwindled, new blends like Norway’s Troll have been added to the cocktail, giving traders in Europe and around the world the most reliable tool to gauge the value of different crudes.

Outside of the North Sea basin, different crude blends that include streams from the US, West Africa and even Kazakhstan could be added to the mix in the future, but irrespective of their origin, dated Brent continues to put Britain at the heart of a $1.7 trillion industry surrounding oil and gas. Importantly for Britain’s future outside the EU, it is a corner of commerce increasingly tilting towards meeting rapidly growing demand in Asia and especially China, the world’s biggest importer of crude.

For example, the Hound Point terminal on the Firth of Forth exported almost 11m barrels of Forties crude in October, the vast majority of it heading to South Korea and China. If Britain is to succeed outside the EU and strike lucrative trade deals with Asia’s biggest economies, North Sea oil could be a useful bargaining chip our European neighbours don’t have at their disposal.

Neither is the North Sea’s story as a major oil-producing region over. The latest figures released by the Oil and Gas Authority (OGA) yesterday identified almost 5.5bn barrels of oil equivalent still to be produced, enough to sustain output at current rates in UK waters for the next 20 years. However, the total scale of oil and gas around Britain’s shores could be far greater, with the OGA estimating there are up to 20bn barrels of oil equivalent discoveries and undeveloped resources still out there.

Of course, tapping these resources in the North Sea is the challenge. Post Brexit it is essential for whoever sits in power in Downing Street to maintain the competitive tax environment vital to encouraging oil and gas operators to continue exploring for resources and more importantly putting new finds into production. The crash in oil prices, which began at the end of 2014, triggered a severe cutback in investment across the North Sea. Globally, spending in upstream oil and gas is expected to drop to around $500bn (£380bn) this year, from a peak around $950bn four years ago. This has made it harder for the UK to compete for investment from the international oil industry.

These pressures will only grow after Brexit, but North Sea oil should still give Britain the cash generating power to defend its economy and the leverage to build new trading relationships overseas.

Andy Critchlow is head of energy news for EMEA at S&P Global Platts