The Streets that Made the Century: Abbey Road, London

For a zebra crossing, it is a curious assertion, "I am the walrus". There is plenty more nonsense, such as, "We are the eggmen", splashed around on the white stripes and yellow globes of the Belisha beacons. Worryingly, some graffiti allude to the Spice Girls. But that is what you must expect at the most famous pedestrian crossing in the world.

For a zebra crossing, it is a curious assertion, "I am the walrus". There is plenty more nonsense, such as, "We are the eggmen", splashed around on the white stripes and yellow globes of the Belisha beacons. Worryingly, some graffiti allude to the Spice Girls. But that is what you must expect at the most famous pedestrian crossing in the world.

It was 30 years ago tomorrow that the iconic image was captured. By the summer of '69, the Beatles were fragmenting, with some acrimony. In seven years of stardom they had moved from lovable pop moptoppery to the precarious front line of rock'n'roll. In the creative process, John, Paul, George and Ringo had destroyed many relationships - including their own. The final Beatles album on which they were to collaborate needed a title, and a cover. There was no stomach for the brave experimentation demonstrated in two previous albums: the extravagance of the 1967 Sergeant Pepper's Lonely Hearts Club Band, and the minimalism of 1968's White Album.

As the most productive partnership in music disintegrated, the band wanted to keep it simple. So the album was named after the place where they recorded it. And as for the cover? Why don't we do it in the road, to quote from bold black felt-tip scraw on the wall of number 3 Abbey Road.

At first sight, this leafy lane in St John's Wood, north London, is a surprising choice for stardom. A mere backstreet compared with the noisy arteries of Maida Vale and Finchley Road that sandwich it, Abbey Road is barely a mile long. It originated as the lane leading to Kilburn Priory, hence its name.

Start at the West Hampstead end, where Abbey Road makes a brief foray into the Borough of Camden and NW6; most of it resides within the more desirable borders of NW8 and Westminster.

As you move south-east from the West Hampstead end, nothing distinguishes it from other St John's Wood streets. A council estate soon gives way to mansion blocks of flats, and handsome detached villas that are mostly divided into apartments.

Suddenly, at the last-but-one house at the end of this short and winding road, you stumble on the source of its celebrity. The rear of a large property at 3 Abbey Road has sprouted a veritable carbuncle that resembles a large, brick cinema. These clumsy walls have reverberated to the recordings of Edward Elgar and the Spice Girls (not, thankfully, at the same time). But every tourist arrives to pay homage to a band who lasted barely a decade and broke up 30 years ago.

EMI, which owned the Parlophone label, brought the Beatles here to record their first hit, Love Me Do, in 1962. Even when the band set up their own label, Apple, they continued to record in Studio 2 under the direction of the (recently knighted) producer George Martin.

The equipment was prehistoric by modern standards: none of the digital tricks of today's trade, just a couple of BTR-2 tape recorders the size of Mini Coopers. Yet here they created a canon of music that obsesses people who were not even born by 8 August 1969.

At 11am that day, the photographer Iain Macmillan climbed a stepladder set up in the middle of Abbey Road. The location was just south of the zebra crossing that was about to become the most celebrated pedestrian span in the world. Eight be-flared legs strode across in formation, away from the studio and towards the memorial to Edward Onslow Ford, RA, "erected by his friends and admirers", that stands just out of the picture.

A street sign appeared on the rear of the album cover, and promptly took over from Penny Lane as the most sought-after trophy among devotees. You can now buy a replica at the Abbey Road Cafe, price £20. The high-school students from Independence, Missouri, who turned up en masse on Thursday morning, made do with 50p postcards of the famous image.

"Did they stop all the traffic?" asked one. I assured her that British motorists are happy to halt at zebra crossings, then winced as two vans and a taxi failed to do so while the US visitor tried to cross. The traffic stopped for Anthea Turner, though; the TV presenter was there with the tribute band the Cavern Beatles to promote Going for Green, an environmental charity.

The fans arrive in their hundreds every day. Some take part in organised tours, others shyly approach the once-white front wall to read or add to the scrawls that adorn it. And then they annoy the hell out of cabbies and the driver of the 139 bus by crossing the road in the manner of the Beatles.

Simple expedience dictated the choice of the album cover, but everything the Fab Four did was accorded deep significance. All kinds of myths began to spread on the world wide web of Beatles fans, centring on the fact that Paul was wearing no shoes. Clues on Sgt Pepper's cover had "shown" that the bass player was already dead.

That these rumours were exagerrated is shown by Sir Paul unveiling this week the album he recorded at 3 Abbey Road, a handy location for the home he is said still to own at 7 Cavendish Avenue, a quarter-mile east from the studio.

On his walk between the two, he could call in at the Abbey Road Cafe, which is built into St John's Wood tube station and hence some distance from the street. It opened earlier this year, and dispenses Abbey Road merchandise (best seller: a T-shirt, £18.99) along with cappucino. "Most of our customers are American and Japanese," says the manager, Paul Hodgkinson.

The graffiti demonstrate that Abbey Road disciples come from all over to survey the Beatles' last days at the end of the road. The plainest message is from one Edgar Rivera, of Veracruz in Mexico, "I said I would, and I did".

Getting there: for the north-west end, take the Jubilee Line tube to West Hampstead. Turn left out of the station and walk for half a mile down West End Lane, which runs into Abbey Road. For the south-east end, and the Abbey Road Studios and zebra crossing, take the Jubilee to St John's Wood. From the station (which includes the Abbey Road Cafe), cross Finchley Road and walk down Grove End Road until you see the crossing. Bus 139, which begins in Trafalgar Square, and bus 189, from Oxford Circus, run the length of Abbey Road.

Organised tours: there is no public access to the studios themselves. Beatles Walks (0171-434 0459) and the Original London Walks (0171-624 3978) run tours of Beatles' locations in the capital, culminating outside the studios at Abbey Road. Beatles Walks is organising an "Abbey Road Day" tomorrow, with a variety of tours.

Abbey Road Cafe: open 7am-7pm.Websites: www.abbeyroad.co.uk; www.abbeyroadcafe.com; www.beatlesforsale.demon.co.uk