But since the first section opened between South Mimms and Potters Bar in September 1975 the roads that became the M25 have enabled people to get from A and B at speeds that would have been unimaginable to their parents. At over 100 miles, it is now the biggest such orbital road in the world, after the Berliner Ring. And, when it comes to property, it is no exaggeration to say that it has transformed the south-east.
And there is now an additional premium attached to proximity to the M25.
People may not boast about living near the M25 with the same gusto as they boast about living in a conservation area or an area of outstanding natural beauty, but they certainly count themselves lucky.
And now, thanks to detailed research by Hamptons, it is possible to quantify just how lucky some of them actually are.
About a quarter of a million people live within a mile of a junction of the M25 and in many cases they have seen property prices in their area far outstrip rises in similar towns further away from the motorway.
In South Mimms, at Junction 23, the start of the A1, the average property price in 1975, when that stretch of the motorway opened, was just £15,000. It is now £360,000, an increase of 2,256 per cent.
The comparable increase for the UK as a whole is just over 1,600 per cent. Potters Bar, at Junction 24, and Reigate, at Junction 8, are two more winners, with price rises in excess of 2,000 per cent over forty years.
Potters Bar, Junction 24: five-bedroom home with 150ft garden. Price: £1m. Agent: Hamptons; 01727 400 223
You would hardly call South Mimms a desirable address. All it is known for – and with no great affection – is its heaving service station. But the Hamptons figures speak for themselves. The M25 has been as big a gamechanger as those new mainline stations that can suddenly add a nought to the value of a property.
Geographically, there is no clear pattern in the figures. The two “top” M25 towns, i.e. those with the highest property prices, are diametrically opposite each other on the ring – Wisley in Surrey, at Junction 10, and Theydon Bois in Essex, at Junction 27. Average house prices in the two towns are £870, 000 and £868,000, respectively.
Brentwood, Junction 28: Ingrave Hall is an early Victorian farmhouse sitting on about 7 acres with 7 bedrooms. Price: £3.25m. Agent: eMoov; 0333 1214950.
But it is surely significant that, in both cases, there are also excellent rail links into London – and that road usage on the M25 itself during the rush hour is actually falling. Only 17 per cent of commuters into London from Wisley use their car, compared with 64 per cent from Addlestone at Junction 11, just a few miles to the west.
Addlestone and Thorpe, at Junction 12, have some of the heaviest rush-hour traffic on the whole M25, which you would think would count against them as desirable locations. In fact, the opposite seems to be the case.
Chorleywood, Junction 18: a modern mansion in a semi-rural setting with four bedroom suites. Price: £3.15m. Agent: Hamptons International; 01923 375332.
Property prices in Addlestone and Thorpe have risen by 26 per cent and 29 per cent respectively in the last 12 months – the highest figures on the motorway.
“It seems clear from the data that living near a busy junction does not seem to affect house price growth,” says Fionnuala Earley, the residential research director at Hamptons.
“The statistics also indicate that the M25 is used to get around London as much as, if not more than, to get into it."
Will those home owners who have reaped the benefit of the M25 still feel the same attachment to the motorway in 2025 when, if present trends continue, there will be so much traffic on the road that commuters will be eating their take-away suppers on the hard shoulder?
Rush-hour traffic at Junction 14, Poyle, by Heathrow Terminal 5, has increased by 76 per cent in the last 10 years. There have also been increases of more than 30 per cent at Junction 5, Chevening, Junction 6, Godstone, and Junction 15, Colnbrook.
Reigate, Junction 8: a large detached, family house with five bedrooms on a private road. Price: £1.795m. Agent: Hamptons International; 01306 580 182.
Everyone can see there is a problem, particularly to the west of London, where the M25 meets the M40, M4 and M3 in quick, or often not so quick, succession.
But attempts to widen the motorway have run into planning difficulties, and only a raving optimist would be confident that driving around London will be less stressful in the foreseeable future.
But on the occasion of the motorway’s fortieth anniversary this month, one can at least raise two and a half cheers for the men and women who gave birth to it. Compared with the notorious Boulevard Périphérique in Paris, the M25 is far enough from the centre of the capital to ease traffic congestion without doing irreparable damage to the green belt.
Bricket Wood, Junction 21A: a four-bedroom home surrounded by woodland and with ample parking. Price: £1.2m. Agent: Hamptons International; 01727 400223.
It is customary to regard “inside the M25” as synonymous with Greater London, but in fact there are still villages inside the motorway that have an almost rural feel – such as leafy Chipstead in Surrey. There is a surprising variety to the motorway’s hinterland.
And if estate agents stifle a smile when they write “benefiting from fast road links such as the M25” in their brochures, at least they are telling half the truth.