Jan Cramer, the wonderfully talented narrator of almost all of my audiobooks, is a Cockney by birth: born in the sound of the Bow Bells.

You wouldn't know it to listen to her narration; she has a neutral English accent, which can transform into a variety of regional accents when the dialogue requires it. But Jan's place of birth means that she particularly enjoys narrating the London Cosy Mysteries series.

I met up with her recently and she asked me a question. “As a Brummie, how come you know the streets of London so well?” She'd been narrating one of the books and had been impressed by the detail and accuracy of Diana and Zaf's walks across London.

Diana Bakewell, the star of the novels and an experienced London tour guide, adores her home city. She, like Jan, was born within the sound of the Bow Bells and has lost her cockney accent- although her mum, TK, still has the distinctive East End accent.

Diana loves travelling around her city. She loves doing so in the Chartwell and Crouch vintage tour bus, and she particularly loves doing so on foot.

Her sidekick and fellow tour guide Zaf, by contrast, doesn't know the city so well. When the series opens, he hasn’t long moved to London from his home city of Birmingham. London feels strange and new, and very, very big. But Zaf is someone who grabs life by the horns, and he finds the strangeness and newness exciting.

But Zaf doesn't walk because of a fondness for the city. He walks because he's skint. As someone with the relatively low income of a trainee tour guide and no means to afford a home in London, he'd rather walk than pay tube or bus fare.

So both Diana and Zaf do a lot of walking. They walk with their clients, guiding them around sights that aren't accessible by bus. They walk from Diana's home in Pimlico to the bus depot on Marylebone – a significant walk that most wouldn't do as part of their commute. And they walk to let off steam, sometimes conducting arguments as they stride past London's landmarks. At one point in Death in the West End Zaf, unable to afford cab fare, walks all the way from Primrose Hill to Pimlico, a distance of four miles. Not far for a country hike but Zaf is simply getting from A to B – and he has to fight his way through the crowds.

And the reason that Millie Ravensworth (aka Heide Goody and Iain Grant) and I were able to describe all those London locations so faithfully is because we also walked. A lot.

I've been walking around London for over 30 years. As a child, family visits to the capital would always involve tube or cab rides (never bus); my parents just wanted to get where they were going as quickly and easily as possible. But then I made my first solo visit when I was 20, and I discovered the joy of exploring London on foot.

On that day I started at Oxford Circus, if I remember rightly, and headed south. My route took in a plethora of sights I had never realised were so close together, because I'd always travelled between them by tube.

I strolled down Regent's Street, dodging the crowds (it was a weekday, but it was August). I then found myself at Piccadilly Circus, where I shopped to look at the statue of Eros (which features on Death in the West End.) In recent years I've discovered back routes and shortcuts that let me avoid the crowds of Piccadilly Circus, but on that day it was a revelation, and part of my adventure.

My route took me onwards, through Theatreland and towards Trafalgar Square. Again, I was amazed by how close the sights were. If you take the tube from Piccadilly Circus to Charing Cross (the closest station to Trafalgar Square), it probably takes just as long as walking once you've trudged through all the tunnels and fought your way through the crowds. And if you take the bus you'll get stuck in traffic (although it is a nice way to do some people-watching if your feet are weary or you're not so mobile).

I paused to trail my fingers in the water at the base of the fountains and to dodge yet more crowds (easier now that some of the roads around Trafalgar Square have been pedestrianised or removed), and continued.

Now, remember that this was the early nineties. I had no smartphone – no mobile phone at all, not for another three years – and no Google Maps. I was reliant on the maps at bus stops and my sense of direction. And the buildings I could see in the distance, because from Trafalgar Square you can see right down Whitehall, towards the Houses of Parliament and Big Ben.

So I continued.

Eventually I found myself at Westminster. I paused to dip inside Westminster Abbey and enjoy the cool air inside, and then bought an ice cream from a van outside. And I took a look at the Houses of Parliament and probably didn’t take any photos, as I doubt I’d have been carrying a camera – smartphones definitely have their advantages.

Little did I know that ten years later I would be working in Westminster and regularly walking (sometimes running) along the banks of the Thames between meetings. But that’s a story for another time.

By this time I was foot-sore and decided to hop onto the tube and back home. But it was the first of many strolls round London, which have taken me hundreds of miles around the capital in the years since.

I may not know London as well as Diana Bakewell does, but I’m slowly getting there.