The M25: We're on the road to nowhere

Twenty years ago Britain gained a new road - and a new national institution. David Wilkins goes round in circles on the M25

The M25 is more than a motorway, but what is it? Or in the questing words of Iain Sinclair in his book about it: "Was this grim necklace the true perimeter fence? Did this conceptual ha-ha mark the boundary of whatever could be called London? Or was it a tourniquet, sponsored by the Department for Transport and the Highways Agency to choke the living breath from the Metropolis?" I prefer the answer given by the satirists Terry Pratchett and Neil Gaiman. "Many phenomena - wars, plagues, sudden audits - have been advanced as evidence for the hidden hand of Satan in the affairs of Man, but whenever students of demonology get together, the M25 London orbital motorway is generally agreed to be among the top contenders for exhibit A."

But then, there's lots they don't know about the M25....

PENSIONER BLOCKS MOTORWAY

Quite the opposite, in fact. On 29 October 1986, the Prime Minister, Margaret Thatcher, opened the M25 (between J22 and J23 (London Colney and South Mimms). She wore Aquascutum. She said: "I can't stand those who carp and criticise when they ought to be congratulating Britain all over the world." The first break down followed shortly, at 11.16 am.

NEW MEETS OLD

At the Chalfont Viaduct, where the M25 threads through its arches. The Viaduct is a five-span blue-brick railway viaduct built at the turn of the century to cater for commuters travelling from London to High Wycombe on the train.

WIDER STILL AND WIDER

The M25 was designed with a capacity of 100,000 vehicles per day, which it exceeded within a year of opening. Hence the constant proposals for widening. Most is still six lanes, with some four-lane, one 10-lane stretch, and one 12-lane stretch.

BUSIEST BIT...

...is between junctions 13 and 14, with traffic to and from the M3, the M4 and Heathrow. The AA states that 250,000 vehicles per day travel along here, which is twice the design capacity of this section. Has been widened to try to cope.

ROAD TO HELL

The M25 doesn't have the iconic status of America's Route 66, but it has inspired songwriters, if not always positively. Chris Rea's "Road to Hell" for example, is said to refer to the M25: "On your journey cross the wilderness/From the desert to the well/You have strayed upon the motorway to hell."

POLICING...

...is carried out by an integrated policing group comprising the Metropolitan Police plus the Thames Valley, Essex, Kent , Hertfordshire and Surrey constabularies.

LEVELLING UP

Birmingham's "Spaghetti Junction" still sets the standard, but the M25 has some impressive interchanges too. The intersections with the M1 and M23 are especially notable for their awesomely complicated four-level structures.

CIRCULAR ARGUMENT

The M25 (117 miles long) is often considered the world's longest bypass but the A10 "Berliner Ring" Autobahn is longer, at 121 miles. That's a special case, though - East German road planners didn't have the option of building through West Berlin.

CLACKET LANE

The M25 has traditionally been short of service areas. There are now three - South Mimms, Thurrock and Clacket Lane - on the eastern side, but you can still go hungry driving the western half, which is completely bereft of such facilities.

JAMS TOMORROW

Planning for such an intrusive road was difficult and to help things along, junctions were dropped in all over the place to please local residents. That helped the M25 to be built, but allowed lots of local traffic on to what was intended as a long-distance route. It also means the road is now used by many commuters.

MIDAS TOUCH

The busiest western sections of the M25 pioneered Midas (motorway incident detection and automatic signalling) in the UK, a system of variable speed limits and information signs designed to combat congestion.

ORBITAL

Orbital was an English techno duo formed in 1989, consisting of brothers Paul and Phil Hartnoll (born 9 January 1964). The Hartnolls took the name of their band from the legendary raves that occurred in the late 1980s around the M25.

NORTH CIRCULAR

The M25 is the main product of the ambitious London "motorway box" plan of the Sixties which foresaw a series of concentric "ringways" . London's main traditional ring route, the A406 North Circular, was also part of the "ringway" scheme.

SOUTH CIRCULAR

Unlike its north London counterpart, the A205 South Circular Road never got the investment it would have received as a ringway and follows existing streets. The old jibe that it is merely "a collection of signposts in south London" remains true.

JAM TODAY

Politicians avoided making their usual promise about jam today when it came to the M25, but we still got the so-called "largest car park in the world". We have heard of five-hour waits, but despite the moans, journey times would be longer without it.

NORTH OCKENDON

Is the only settlement in Greater London to be outside the M25.

THE OLDEST PART...

... of the London orbital route is the first bore of the Dartford Tunnel, opened in 1963. That was joined by a second bore and the Queen Elizabeth II Bridge, completed in 1991. Collectively these now form the Dartford Crossing. Technically, the M25 is not a complete circle: it ends shortly before the crossing on each side of the river. The crossing itself is the A282.

FASTEST LAP

Ever since it opened, the circular layout of the M25 has, according to urban myth, provided a magnet for racers looking to set the best "lap" time. Presumably, armed with a 250mph Bugatti Veyron you could circumnavigate the 117 miles in 28 minutes, if you encountered no other traffic. Speed cameras might inhibit you, however. Peugeot claimed in 2002 that a 206 diesel could do the circuit on £5.57's worth of diesel. When it comes to speed, you'd better stick with the computer game M25 Racer.

ROAD TO PROSPERITY

There is no official estimate for the cost of the M25 because of the haphazard way it was planned (and it's still being built). Initial tenders for construction were £631.9m and most experts take the final cost to be about £909m up to 1986, or £7.5m/mile.

LITERARY CIRCLES

Or, something to read while you're waiting for the traffic to move. Iain Sinclair's London Orbital is a dark account of a journey on foot around places "where the poor and the mad of the city were dumped". Roy Phippen's Travelling M25 Clockwise is more orthodox.