A national system of road numbers that radiate from a central point would suggest the existence of… well, a central point. But if you go looking for it you’ll find it doesn’t exist.
We’re spending 2023 celebrating the centenary of road numbering. A- and B-roads have been with us for a hundred years now, and to mark the occasion we’re publishing a whole series of new blog posts and updated articles about the numbering system.
If you’ve read our article on road numbers (and we hope you have, it’s brilliant) you’ll know that A- and B-road numbers in Great Britain are allocated according to zones, which are bounded by the single-digit A-roads 1 to 6, and which all centre on London.
You’ll have to forgive me, though, because we’re starting our search for the central hub of all UK road numbers by visiting Spain.
En media de la nada
If you ever find yourself in Madrid, you may well pass through Puerta del Sol, a semicircular plaza at the heart of the city and a major hub for the Metro network. It’s a handsome space bristling with statues and lined by some grand institutions, including Madrid’s central post office.
Outside the post office building, you can find something remarkable. Set into the pavement is a marble plaque with brass lettering that marks Kilometro Cero, the point from which all distances to Madrid are measured, and also - as the map on the plaque makes clear - the hub for the six main national highways that radiate from the capital to the provinces.
Spain cares so much about those first six highways (even though they are mostly superseded by motorways now) that it traditionally uses Roman Numerals to distinguish them. Carreteras Nacionales I to VI begin here, at the centre of the Spanish road network.
You might think such a thing would be esoteric to the point of tedium, but it’s quite a famous spot, and if you spend any time in Puerta del Sol you’ll see a steady stream of people finding their way there to photograph it. You’ll even see tour guides pause there to explain its significance. Kilometro Cero is clearly important.
Fit for a king
Here in the UK, of course, we have our own capital city with six national roads striking out to the provinces, and they are even more significant here because they form the basis for the allocation of all other A- and B-numbers in England and Wales. So where’s our Kilometre Zero?
We do have one, as it happens, complete with brass marker. On the south side of Trafalgar Square, in the middle of a roundabout, and at the foot of the statue of Charles I, you can find another engraved plaque, proclaiming that this is the point to which all distances to London are measured.
It’s not the central point of the road network, though.
For one thing, no numbers of significance converge here. The A4 passes through the roundabout, meeting the A400 and A3212, but that’s it. And for another thing, it didn’t exist a century ago when road numbers were allocated. Our Mile Zero was created in the early 1950s to simplify signposting; for centuries before that, distances to London were measured to one of seven obscure points depending on where you were coming from.
Trafalgar Square is in Westminster, of course, which is far from the oldest part of London. The true historic centre is in the City. That’s where we will look next.
You shall not pass
Pull out a map and you’ll see a dense web of A- and B-roads that converge on the City. That’s no surprise: it is, and always has been, the absolute heart of London.
The City is like nowhere else. It is not a London Borough, but a city within a city, forming a county in its own right, and administered by a Corporation that is unlike any other government body in existence - one that was first incorporated in the Anglo Saxon era. Its extraordinary status and powers were hard won from the monarchy over centuries and it fiercely guards its independence.
Needless to say, if the City is used to standing up to Kings, road numbers never stood a chance. In 1923, when numbers were first introduced, London bristled with them, but they all stopped at the City boundary. Numbering was originally about funding, and since the Ministry of Transport supplied no funding to the City, it had no powers there, so numbers were unnecessary.
Several numbered routes pointed meaningfully into the City, stopping dead at the dragon statues marking the line of the Roman city wall; the A201 and B500 both vanished and reappeared elsewhere as they skirted the boundary.
The focal point of London’s roads was clear: the Bank, a six-way junction situated between the Bank of England and Mansion House, and a point with at least the illusion that roads are converging from all directions. But it couldn’t be the hub of the numbering system, because historical accident put it in the City, a place where numbers didn’t exist.
Without a hub they could get to, the Ministry’s planners had a free hand to do whatever was convenient. As a result, some single-digit A-roads headed directly for the City, and the A1, A3 and A4 all made it to the dragons. Others stopped short for convenience. The A2 ended on the A3 in Southwark; the A5 stopped on the A40 at Marble Arch; and the A6 only began by branching off the A1 in far away Barnet.
Bank on it
At some point in the early twentieth century, things changed, and the City gained road numbers. But they were now an afterthought, and in any case, the City’s ancient streets do not form a meaningful pattern, so the numbers at the boundary were extended inwards in whatever way seemed to make sense.
The history, and London’s disorderly street plan, made it entirely impractical to bring the roads A1 to A6 to the Bank. It simply didn’t work. So while Bank is arguably the true centre of the British road network, it was never Mile Zero and it was never the one focal point for all road numbers. And yet it was, still, the closest thing we had to a hub for the road numbers and their zones.
The only single-digit A-road that ever reached the hub was the A3. It approached up King William Street, and at Bank it found the A10, A11, A40 and A501.
Where was everyone else? This was supposed to be the grand union of the single-digit A-roads and the hub of six numbering zones. What had happened?
The A1 sent apologies from St Paul’s, a stone’s throw west, where it terminated on the A40. The A2 stayed south of the river, from where the A3 took over. The A4 got very close, but didn’t have very good aim, passing by to the south and finishing on the A3 at Monument. The A5 already ended miles to the west at Marble Arch and made no effort to come closer. And the A6, of course, had never been invited to the party at all, and started in a small town in Hertfordshire.
The picture with regards to zones was even more silly. Zone 2 lay entirely south of the Thames, so wasn’t involved; zones 5 and 6 were both further west thanks to the distant beginnings of A1, A5 and A6. Zone 3 was kept at bay south of Cannon Street by the A4. So the only two zones that did make it to Bank were 1 and 4 - but neither of the roads with matching numbers came to the junction, so the boundary between zones 1 and 4 was marked, at Bank, by A3 and A40.
Road numbering is really silly when you look at it close up.
Breaking the Bank
The situation described above persisted until the early 1990s, when the City became a target for IRA bombs and security was increased. A security cordon called the Ring of Steel was installed around most of the City. Streets were narrowed and checkpoints were built - many still exist today. To discourage through traffic from streets that were now blockaded with vehicle checks and chicanes, most roads within the City were declassified, losing their numbers and their status.
The result, rather like in the 1920s, is that most road numbers stop before they reach the dragons. The A1 and A40 have a shared terminus at London Wall, while the A4 takes a sideways lurch off Fleet Street to travel up Fetter Lane to end on the A40. The A10 has been rerouted to end at the Monument, where it meets the A3 head-on. The A11, meanwhile, has been banished to Aldgate and the A501 gives up at Moorgate.
The people responsible for making the Ring of Steel changes weren’t thinking about road numbering, of course. They were mainly thinking about terrorist bombings, and that’s fair enough; even those of us who think very deeply about road numbering would find it hard to argue with their priorities. But if we do stop to ask what happened to the numbering zones those roads used to mark, the answer is that nobody knows. It simply wasn’t a consideration in the 1990s.
It’s not a consideration now, either: the only purpose of the zones is to help select new road numbers, and nobody is going to bring road numbers back to the City. Realistically there’s no need for zones in the middle of London.
Today, the situation is changed again. The City is actively working, year by year, to rebuild its ancient streets, sweeping away layouts that were provided in an era of car dominance and providing environments that put pedestrians and cyclists first. The Bank itself is part of that: the horrendous casualty rate among cyclists and pedestrians at the junction prompted the sudden banning of motor traffic a few years ago. Between 7am and 7pm, it is open only to pedestrians, cyclists and buses, and at the time of writing work is happening at the junction to widen pavements and make those changes permanent.
For all the talk of a numbering system with a central hub, it turns out that we never had any such thing. It began in 1923 with a hole in the middle of London, and today once again the zones don’t meet: they just sort of fade away as you get close to the City. There is no middle, just the middle of nowhere.
The Bank, of course, is still there. Shall we pay a visit?
A trip to the Bank
Bank Junction today looks much the same as it always did, regardless whether the streets meeting there have numbers. But let's take a look at the innocuous streets that once formed the central point of the road numbering system.
A good article, though I must advise that one teeny part is incorrect:
"Its extraordinary status and powers mean that the ruling monarch may not enter the City without the Lord Mayor’s position."
There is a ceremony involving the monarch and the Lord Mayor when the monarch enters the City, but in no way does the monarch require the Lord Mayor's permission. Even if it were true, the final word should be "permission" not "position".
Thanks for this correction - a bit more research than I did at the time shows you're quite right! I've reworded the offending passage to something more suitable. The myth about the monarch requiring permission to enter is quite widespread; Wikipedia has a decent summary for those who are interested.
What an interesting article, it would make a good item on QI. As for the King or Queen entering the City of London, because of all the ceremony involved thats why traditionally if the Monarch is going to Sandringham by train they use Kings Cross and not Liverpool Street.
NOT TRUE - any more - it used to be the case.
But it was changed ( During WW II - I think )
I remember seeing our late Queen pass through Liverpool Street in about 1959, on her way to Sandringham
Hi! I enjoy reading about your articles, but, as a madrilenian, I have to add a small correction worthy of Pedants' Corner in Private Eye: The building sitting in Puerta del Sol is no longer the central Post Office, and it hasn't been for a century, even if the building is still named after it. It's now the seat of the State Government, which, to some degree, is an even more important institution.
Thank you for all that information! I adore reading about historical leftovers of this kind.
Hi Victor - thank you for the correction! I didn't know this, but you're right, it's even more appropriate that it marks the zero point.
Is this the (rich, privileged) City pushing polluting through traffic on to the poorer streets of Tower Hamlets and Islington by any chance?
Through traffic continues to pass through the City on Upper Thames Street and London Wall as it has done since the 1950/60s.
Yes, the City (like many other London boroughs) is actively working to make a safer, cleaner and less car dominated environment - a much more pleasant place to work and live!
The reason for the monarch travelling for decades from London to Sandringham via Liverpool Street was simply that it was the Great Eastern Railway which operated the whole route. Trains from King's Cross as far Cambridge ran long ago, but that only became the route used by through trains after electrification beyond Cambridge to King's Lynn was completed in 1992. JM
This article is on a subject that only the hardest core of hardcore geeks would have the remotest interest in. Yet it's testament to the glorious tradition of the Great British Eccentric that it exists. And all power to you for that!
PS The links to the bigger pictures are broken :-(
Really? I've heard people ask before why all the roads around them are numbered A4xxx and why they drive somewhere else they all start with a different number. I think the idea of road "zones" is one of the easier things to explain compared to say, ringways when they ask why the M25 is so obviously weird in places.
"Well, there were originally meant to be four motorways, the inner two of which were never built, although there is plenty of evidence on the ground. The M25, however, is a combination of the third and fourth motorways, which you can see..."
The middle of nowhere translates as "En medio de la nada" instead "El media de la nada"
As a truck driver I really love this interesting website. Thanks to everybody here!
Thanks Alex - my schoolboy Spanish only takes me so far! I’ve corrected this now.
I have to wonder if having a defined center and/or 0 milepost/km for major highways is more or less common across countries around the world.
I know here in the US, there isn't really one due to the way our highways are usually numbered and mileposted (though one could probably make a pretty reasonable claim that, despite being the southEASTern-most point in the highway grid, MP 0 on US 1 in Key West, FL, is the "start" of the US Highway System). Amusingly, there does exist an official "Zero Milestone" outside of the White House in Washington, DC, which, when placed in 1919, years before the current US Highway System was even a thing, was intended to be the distance from which all highways in the US would be mileposted, directly inspired by Rome's Golden Milestone.
These days, it just kind of exists, largely ignored by the highways that developed in this country, but one can very much still go visit it.
In Penwortham (on the A59 just to the south of Preston) there were at one point 3 signposts to Southport and they had different distances. And it turned out that all were correct! It was simply down to the fact that the distances were all measured from different points and were to different points in Southport.
Isn't there a case for placing the "hub" of the zone system at Monument? It was, if I understand correctly, the point at which zones 1, 3 and 4 met. Everything to the east of the A3 was in zone 1; everything to the west of the A3 but south of the A4 was in zone 3; and everything to the west of the A3 but north of the A4 was in zone 4.
As you point out, that anomalously made the boundary between zones 1 and 4 north of Monument the A3 (and subsequently the A40) when you might have expected it to be the A1; but it was no more anomalous than treating the A40 as the boundary between zones 4 and 5 from St Paul's to Marble Arch, a much longer distance.
If the principle of "zone boundaries are always the single-digit A-roads" had been strictly adhered to, we might have seen the A1 running all the way to the Monument via Cheapside, Poultry and King William Street.
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- Photograph of plaque marking Kilometro Cero is taken from an original by Kaetzar via Wikimedia Commons and used under this Creative Commons licence.
- Photograph of Borough station in 1982 is taken from an original by Ben Brooksbank and used under this Creative Commons licence.
- Map of Bank with road numbers is from Esso Road Map No. 1, undated, believed to be out of copyright.
- Map of Bank today is © Openstreetmap and contributors.