No one thinks twice today about reaching for a map to navigate their way around a town or city - but do they stop to consider how the street atlas came to be?
When Phyllis Pearsall set out for a party in Belgravia, London, on a rainy night in 1935, she took along the most recent Ordnance Survey map to help her.
But the 16-year-old map failed to stop her getting lost. And by the time she arrived at the gathering, hours late, bedraggled and wet, she resolved to do something about it.
The result one year later was the first edition of the A-Z Atlas and Guide to London and Suburbs.
Pearsall fans and former colleagues celebrate her 100th anniversary today. She died in 1996, just short of her 90th birthday, and still working at the company that makes the definitive guide to London, other UK cities, counties and areas in 359 titles.
The first edition was a year's work
Creating the first A-Z was a tough job. Before satellite imaging or extensive aerial photography, Pearsall worked 18-hour days and walked 3,000 miles to map the 23,000 streets of 1930s London. She had just one colleague, draughtsman James Duncan.
Of course, there were no decent maps to follow. "I had to get my information by walking. I would go down one street, find three more and have no idea where I was," she later recalled.
Pearsall was an artist first and the map-making was intended to fund her primary passion. At the start, however, it was the other way around and her commissions funded wages.
The struggle to have the atlas published showed the mettle of a woman who was turfed out of home by her mother's lover, and was divorced by the age of 30.
Her completed map was rejected by publishers, so she ran off 10,000 copies and sold them to WH Smith. Pearsall chose the name A-Z from the index. It was a hit publication and, bar a spell in World War II when map production was government-restricted, the company grew and grew.
Mistakes a minefield
Today, A-Z is one of several competing street atlas brands on bookshop shelves. But for anyone with a love of maps, their aesthetic and their complex detail, an obsessional desire to know how places fit together and a deep-seated aversion to being lost, Pearsall's life's work is remarkable.
PHYLLIS PEARSALL MBE
1906: Born Phyllis Gross
1920: Leaves school and spends teens in France
1928: Marries artist Richard Pearsall, they later part
1935: Returns to London and starts the A-Z map
1939: With maps restricted by war, works for Government
1945: Injured in plane crash
1986: Exhibition of her paintings in London
1996: Dies of cancer aged 89
"She was both determined and inspirational, knew exactly what she wanted to do and carried everyone with her," says Ian Griffin, the designer at the Geographer's A-Z Map Company, who worked for Pearsall for 27 years.
The A-Z is "more than direction, it's a history" says Mr Griffin. "Some people are interested in flowers, some people have empathy for maps. There's so much there, it tells you how the city's grown, it's a picture of the world."
The pre-war A-Z of London is a perfect record of the pre-Blitz layout with areas like the warren of booksellers' shops in Paternoster Square - now an open expanse behind St Paul's.
Compare London's Docklands in the 1960 edition to one of today's editions, and witness the immense changes in transport, housing, growing park land and shrinking waterways.
Seeing by road
Design consultant Stephen Bayley says the reason for A-Z's success is simple: "It addresses the real needs of people who live in cities and they just let the roads dominate. The North Circular is given far more significance than Buckingham Palace. We're made to see cities in the terms of the A-Z - in those terms it's a great work of art."
Add your comments on this story, using the form below.
Fantastic! Today most ladies would be more concerned with sore feet, wet hair and blaming someone else. Phyllis should be an inspiration to all women.
Who needs sat nav when you have an A-Z?
Daniel Crisp, London
I wish they'd expand to Germany. Here you can only get street plans of cities in map format, which is unwieldy and doesn't have enough detail, especially for large cities. Anyone who's had to refold a map under a small umbrella or while in the front passenger seat of a car will appreciate what a great idea it was to print the A-Z in book format.
Every motorcycle courier who ever worked in London owes a huge debt to this lady. And the City of London owes an equal debt to the thousands of two-wheeled messengers who have kept the City running for decades, all with the help of A-Z map books.
Thank you Phyllis, my previous life as a motorcycle messenger would have been so much harder without your wonderful maps!
Glenn Le Santo, Lincoln
I always include the London A to Z on my list of favourite books, and I'm dead serious. It's a work of genius and mesmerising to look at, even if I'm not specifically trying to locate an address.
Simon Feegrade, Surbiton, England
I love my A-Z's. I've got through many over the years, it's joined all the dots up for me and enabled me to cycle everywhere from Elephant and Castle to Crouch End, Battersea to Shoreditch. Without it I wouldn't know London like I do. An amazing invention by an amazing woman!
Christine Jones, Ely
Nice story - but it does rather give the impression that Phyllis Pearsall produced the first non-Ordnance Survey map of London. In fact there were attempts before then. I have a copy "The Authentic Map Directory of London and Suburbs" which dates from the 1920's. The maps are very clear and accurate, and Phyllis did not need to tramp thousands of miles drawing her own. The only problem with mine is that it is big (10 inches by 13 inches), so hers was a big advance in convenience.
Robin Puttick, London
It's good to hear that I'm not alone in being a map freak!
Megan, Cheshire UK
But the A-Z maps are awful - practically unreadable. If you've seen a map to an Australian city like Melbourne's "Melways" you'll see a great example of a clear, easy to read map.
Thea Guest, London
A simple but highly effective invention whose longevity is a fitting tribute to its creator's ingenuity.
Dave Wright, Cheltenham, UK
I just looked at a Melways map and I can't say it's any better. In fact, I think they get away with a less sophisticated design because the streets are more spaced out. I can't imagine a better map than the A-Z for the City of London's warren of tiny streets and passages.
I am fascinated by maps and The A-Z is of the best, in a league of its own. Around 1992 I was in Tokyo on business and asked my hosts if there was an A-Z of Tokyo. A long debate ensued and it was concluded that there was no such thing and that it would be impossible because every street has many names changing at each junction. I think that difficulty could be overcome but we are very fortunate in having it. for UK cities.
Howard Longley, Claygate, Surrey
Whenever I travel with a GPS I always keep an A to Z in the boot as it never lets you down. I've never had a battery or system failure with an A to Z.
Peter Curry, Newcastle
Why oh why does every destination have to be on the turn of the page?
Ulrich Zwingli, Coulsdon, UK
When I joined the Metropolitan Police in the 1960's, issued with my uniform, whistle, and truncheon was an A to Z. In the years that followed, the A to Z was by far the most used.
Peter Bolt, Redditch
Phyllis Pearsall's London A-Z is right up there with Harry Beck's London Underground map - both world class design classics which other cities in the world have tried emulating but not quite matched.
The BBC may edit your comments and not all emails will be published. Your comments may be published on any BBC media worldwide.