Diesel prices plunged by almost 17p a litre in June, marking the most significant decline in the cost to fill up between the start and the end of the same month since records began in 2000.

The sizable declines at fuel station forecourts were triggered by a substantial drop in oil prices on the back of a deal between the US and Iran to end the conflict in the Middle East.

This saw Brent crude - the international benchmark - slide from $93 a barrel to $73 over the 30-day period, falling back to the same price at the time the war broke out on 28 February.

At the beginning of June, the UK average price of a litre of diesel was 183.8p. However, by the end of the month, it had tumbled by 16.6p to 167.1p.

This is the largest known fall in the cost of a litre over the course of a single month, beating the previous record by almost 5p. However, prices are still 25p a litre higher than at the end of February. according to RAC Fuel Watch.

For drivers filling up a typical family car with a 55-litre fuel tank, it translates to a £9 saving at the pumps, falling from £101 to just under £92. 

The average price of petrol also went into reverse by 8p in June – the seventh greatest monthly fall in the last 26 and a half years – as UK forecourts slashed a litre from 159.4p to 151.4p. 

It means petrol car owners saved £4.40 per tank at the end of the month compared to the start.

As you can see from the chart above, pump prices are falling more gradually than they increased, despite the Government's introduction of the Fuel Finder Scheme.

This requires operators to be transparent about their pricing by updating the cost of petrol and diesel at their forecourts within half an hour of making changes. This is uploaded into an online database, with the information accessible to fuel pricing websites and apps, such as PetrolPrices.com. 

The diesel pump price drop was even greater at the 'big four' supermarkets - ASDA, Morrisons, Sainsbury's and Tesco.

The average price of diesel dived 19p a litre from 182.4p to 163.3p. 

The unleaded reduction, however, was slightly smaller than the UK-wide one, at 7p.

The price of motorway fuel also fell by nearly 8p for unleaded – 179.8p to 171.7p - but diesel's decline wasn't as steep as that seen across the whole of the nation, only coming down 14p from 201.1p to 187.2p.

Simon Williams, head of policy at the RAC, said that while the savings on motoring-related costs were welcome, drivers are still paying more at forecourts today than they were before the war broke out.

'While diesel dropping 17p in a month is very positive, it's also important to realise that its average price shot up 49p a litre from the end of February to 191.5p on 15 April, which equates to a rise of more than a penny a day,' he explained.

When conflict began on 28 February, the price of a barrel of Brent crude was $73 - the same it is today - and the average UK price of a litre of diesel was 142.4p.  

But he says fuel prices should continue to fall over the coming days.

'Fortunately, the oil price is now in the low-$70s range which is only $10 above the average of the first two months of the year,' he said. 

'At the time the conflict began drivers had average prices of 132p for unleaded and 142p for diesel, so we're still some way off those levels.

'As things stand, petrol should dip under 150p soon and diesel ought to get to below 160p but we would need the price of oil to fall further to see a return to the pre-conflict prices.'