With long queues outside petrol stations, pumps running dry across the country and rumours that the army might be brought in to drive tankers, investigations reporter Joel Adams takes a look at the factors behind a memorable few days.

How does petrol get to the UK?

The petrol or diesel you pump into your car at a petrol station arrives on these shores in the form of crude oil, purchased from oil-rich nations overseas and borne in vast ocean-going tanker ships which can hold hundreds of thousands of tonnes.

The UK has six major refineries which take these shipments, situated around the coast in deep-water ports capable of accepting the tankers.

One of these is in Scotland, at Grangemouth on the Firth of Forth; one is in Wales on the Pembrokeshire coast; two are in Lincolnshire near the Humber estuary; one is in Ellesmere Port in the North West and one is on the south coast outside Southampton, on the mouth of the Solent.

Between them these massive plants refine approximately 60 million tonnes of petroleum products a year.

These refineries are not to be confused with the massive natural gas plant at Bacton in north Norfolk, which brings North Sea Gas onshore and then refines and begins its distribution through a separate network.

Where does petrol go next?

The refined petrol products are transported - by road if necessary but in many cases by pipeline - to a network of 47 fuel distribution terminals around the UK.

In East Anglia these include Asco Oils’ terminal in Great Yarmouth with a capacity of 11,034 cubic metres of petroleum (enough to drive a Ford Focus more than one hundred million miles).

Petrol and diesel is then moved to garage forecourts in tanker HGVs with a capacity of around 36,000L (enough to fill around 700 Ford Focuses), driven by specially trained drivers.

Eastern Daily Press: Drivers queue for fuel at a filling station on the A149 at HeachamDrivers queue for fuel at a filling station on the A149 at Heacham (Image: Chris Bishop)

Why are garages running out?

There is not a shortage of fuel. There is fuel in the refineries, and fuel in the terminals.

However there aren’t enough qualified HGV drivers to get it from the refineries to the petrol stations.

Dr Arijit Bhattacharya, associate professor in operations and supply chain management at the University of East Anglia-based Norwich Business School, said: “People are storing and stockpiling, but the problem is not fuel supply, it’s about a lack of HGV drivers.

“A few months we had the pingdemic, that was the same problem manifesting in a different way.

“This has two causes, one is Covid and the other is Brexit. We have a gap of nearly 100,000 lorry drivers.

“We have nearly 20,000 HGV drivers who have left the UK, and this has caused a certain impact.

“We have a backlog of as many as 40,000 HGV drivers waiting to take their tests, to get qualified.”

These are tests which were cancelled during the pandemic.

A spokeswoman for the Hoyer group, one of the leading employers of specialist HGV drivers in Europe, said across the UK fleet the company had 50 vacancies among 1,200 positions.

So is isn’t just panic buying?

No, there were some outages from the middle of last week, but the numbers were tiny - fewer than one per cent of the country’s forecourts were out of fuel.

Motorists’ behaviour over the last three days has, as it were, fuelled the problem.

One oil company executive said: “Yes we have some driver shortages but you still do have more than 90pc of the deliveries we’d expect to be making in normal circumstances.

“It’s the elevated demand over the last three days, that’s exacerbated the problem and we haven’t been able to keep up with demand.”

Why have garages run out so quickly?

The Petrol Retailers Association warned on Monday that two-thirds of its membership of nearly 5,500 independent outlets were out of fuel, with the remainder "partly dry and running out soon". The UK has a total of more than 8,000 petrol stations.

Part of the problem is that profit margins on retailing petrol are actually very low (most petrol stations make more on the coffee than they do on the fuel) so oil companies operate just-in-time delivery systems to ensure they don’t spend any more transporting the petrol than they need to.

If you refill a petrol station when its tanks are still 10pc full, you'll have to visit 10pc more frequently than if you wait until they've practically run dry each time.

So if demand spikes, there is not a lot of spare capacity in the network. And while capacities of filling stations varies enormously, most can hold enough for only three to seven days’ worth of normal demand - the key word being “normal”.

Eastern Daily Press: Drivers queue for fuel at a BP filling stationDrivers queue for fuel at a BP filling station (Image: Chris Bishop)

Do I need petrol?

You can probably drive further than you think on what you’ve got.

A reasonable average for most drivers to cover is 10,000 miles a year - so that’s just under 200 miles per week.

How often you need to refuel will depend on the fuel-efficiency of your car, and the size of your petrol tank.

The tiny Toyota Aygo gets around 55mpg, which means 12.1miles to the litre, but it only has a 35L tank, so you’ll get 423 miles on a tank.

A Range Rover on the other hand has an average mpg of just 16, but a 106L tank, so a tank will get you 369 miles despite costing three times as much to refill.

In the middle of the pack, a Ford Focus will get 42mpg (9.2mpL) and hold 52L, for a total of 479 miles on a tank.

All of which means a full tank is two weeks of normal motoring for most people - and nobody anticipates actual supply outages to last that long - even if rolling disruption may take months to resolve.

What is being done?

The government has temporarily suspended anti-cartel legislation to let suppliers co-ordinate deliveries to worst affected areas.

It is also trying to rush through HGV tests and has taken the temporary step of increasing daily driving time limits from nine hours to 11.

BP has said it is hopeful fuel stocks at forecourts will stabilise, and start to rebuild during next month.

Eastern Daily Press: No fuel left at the BP garage off the roundabout that joins the A143 and the A146 in Beccles. Picture: Danielle BoodenNo fuel left at the BP garage off the roundabout that joins the A143 and the A146 in Beccles. Picture: Danielle Booden (Image: © Danielle Booden)

On Saturday the government announced a temporary visa scheme for 5,000 foreign HGV drivers to take up employment in the UK until Christmas Eve, but the scheme has faced criticism for not taking into account other pressures and post-Christmas demand.

Longer term, the UK will continue to be a less desirable destination for foreign haulage drivers post-Brexit, with poorer roadside amenities the continental Europe frequently cited as a concern.

For the time being however things are expected to settle down. Gordon Balmer, executive director of the Petroleum Retailers Association, said: “It is unlikely that the vehicles filled over the weekend will need refuelling again soon.

“As a result, we will watch carefully for a possible easing of demand and normalising of forecourt stocks over the coming days.”

Eastern Daily Press: Fuel shortages have forced a number of petrol stations to close this morningFuel shortages have forced a number of petrol stations to close this morning (Image: PA Wire/PA Images)