Looking for cheap accommodation in London? Try camping in a stranger's garden...

If you need somewhere to stay while tackling the 78-mile Capital Ring long-distance footpath, Campinmygarden.com might have the answer.

I was standing on a packed commuter train headed for London with a rucksack strapped to my back and a stranger's address scribbled on a piece of paper in my pocket. Suited business people stole the occasional glance from behind laptop screens and morning papers as I jostled for position while trying to manage my cumbersome load. They were trying to get to work. I was trying to get to my starting point on a 78-mile walk around the capital.

It all began with the launch of a new website called Campinmygarden.com. The idea is that people can register their private gardens as temporary campsite accommodation and users can search for their next left-of-centre bargain break. It's a little like couchsurfing (where homeowners invite visitors in for the night) but without the couch. Browsing the site, it struck me there was an opportunity here for an adventure too exciting to miss. Long on my wishlist of travel opportunities had been the Capital Ring, the long-distance footpath that traces a circumference of London and links together many of its parks, green spaces – and the occasional hidden historic gem. What better way to walk around the city, I thought to myself, than camping in the back gardens of Londoners? I toyed with the stranger's address in my pocket nervously. I was about to find out if I was right.

The route is broken into 15 easy sections, each averaging about five miles, and can be done in any order or combination. The starting point I'd chosen was the south side of Woolwich foot tunnel on the River Thames in east London. From there the Ring follows a clockwise route through Crystal Palace, Richmond, Highgate and Hackney, before running back through the Woolwich foot tunnel and under the Thames to complete the circle.

I headed east beside the river, the sounds of Woolwich Ferry ringing in my ears; just before the Thames Barrier and the O2 Arena, I followed the green Capital Ring route markers on to Woolwich High Street. The path is well signposted throughout but within minutes I somehow managed to get lost and was soon collecting suspicious looks from children on bikes and people peering from behind takeaway chicken shop windows. I must be the first person in the world to have taken a compass bearing on Woolwich roundabout.

Back on route, walking a few miles through Greenwich across Woolwich and Eltham Common, I eventually found myself at Sevendroog Castle, an 18th-century triangular gothic-inspired folly built as a memorial to Sir William James's exploits for the East India Company. Barry Gray, a local doctor and trustee of the castle, told me they were about to start restoration work in order to bring it to wider public attention, and he offered to show me why. We climbed three spiral layers to a turreted roof and suddenly we were above the forest canopy – the city opening around us. I mapped the route of the Ring in my mind, daunted by the scale of it all.

After lunch at the top of Shooters Hill, surrounded by the oaks and silver birches of the 8,000-year-old Oxleas Wood, I walked steadily south, passing Eltham Palace, the childhood home of Henry VIII, before heading down St John's Walk, the old path that links the palace to the hunting estates of the south. Here, I stole glances at the city skyline between rows of houses and grazing horses; it slowly changed its face with the gradual arc of my path.

After Beckenham Place Park the dark clouds that had pursued me ominously throughout eight hours and 18 miles of walking finally broke. I ran through the dinosaur sculptures of Crystal Palace in a torrent of rain, spurred on by the text I'd received from my first garden owner: "Hope you're not too wet, there's a beer with your name on it when you get here."

Despite the text message, it was with some mild trepidation that I stepped through the door of my first stranger's home: the top floor of a large detached townhouse, with colourful rugs adorning wooden floors and a collection of art hung proudly among vaulted attic ceilings. But my anxiety soon faded when I was brought into the kitchen, where a tasty spread of cheeses was neatly arranged beside a selection of designer beers.

The owners of the house, the cheese and the beer turned out to be a naturally outgoing twentysomething couple called Vienna and Rick. We wolfed down Camembert and Stilton, then beer turned to wine, and the conversation flowed from art and music to travelling and why on earth they would want a stranger staying in their back garden. "It's all going in the India fund," Rick told me. "That's our next big trip."

I started to feel quite at home, as if I was round at a friend's house for dinner; except my actual dinner was in two tins in my bag and I still had to pitch my tent. Later, as I scooped spaghetti and baked beans into cold, unbuttered rolls, next door's barbecue struck up in earnest, playing the kind of guilty-pleasure mix of music that only very drunken people enjoy. It was like bad festival camping – and as I was lulled to sleep by the sounds of raucous laughter and distant police sirens, it occurred to me that sleeping in someone's back garden is a bit like being a naughty puppy. I couldn't help but mentally paw at Vienna and Rick's door.

From Crystal Palace the Ring heads steadily west through Streatham, Balham and a seemingly endless parade of leafy residential streets. I began to feel like I was on a suburban treadmill, with the same scenery going past on a loop, no matter how far I walked: Identikit rows of white terraced houses with little manicured gardens and polished cars out front; people chatting on their mobile phones while walking the dog. I felt like Bear Grylls making a guest appearance on The Truman Show. But then, as I crossed the wild, interconnecting maze of paths in Wimbledon Common and the seas of lush spring bracken in Richmond Park, the rain came – in earnest this time. Suddenly, those same people were looking despondently at their blown-open umbrellas, their dogs whimpering behind. They shook their heads at my bedraggled form.

Late in the afternoon I arrived at a two-up-two-down in the suburb of Feltham, west London, and pitched up next to the shed and compost heap. Low-flying jets roared overhead as owner Nigel offered moral support by joining me for a bracing camp-stove brew. We smacked our lips at the after-taste of last night's dinner infused within. A former scout, he said he had a soft spot for camping. I wondered if he was nervous having a stranger pitch up in his back yard. "Actually, if you think about it, it's quite safe because we're inside, we can lock the door," he told me with a mischievous grin. "In some ways, it's the camper who needs to watch out."

Just as I was contemplating another night of soggy beans, Nigel's wife Jackie – a native Singaporean – invited me to stay for dinner. But not just any old dinner. "This is all home-cooked traditional food. You won't find this in a restaurant," she told me, as we sat down to a banquet fit for a king, let alone a poor camper. Fresh skate in chilli paste, lamb soaked overnight in lemongrass, and spicy pork dumplings were just some of the delights.

As I ate, I kept one eye on the tent gathering water through the conservatory window. Nigel told me he'd joined Campinmygarden.com for the noblest of reasons. "We're not doing it for money by any stretch of the imagination," he said. "I think it's interesting to meet different people." And of course it is, but as the camper you're not on neutral ground. You're meeting people who are going about their own lives; in that sense it makes the whole experience slightly intrusive too.

The next day the path continued to ebb and flow between gritty sections of grey commuter belt urbanism and startling wild oases of green tranquillity – the experience of each somehow made more powerful by contrasts on offer. The Tudor ambience of Syon House seemed even more impressive next to the modern high-rises of the A315 which lie on its doorstep. A long stretch of peaceful grassland through Greenford ended in a sudden commuter frenzy outside Sudbury Hill station; the village-like calm of Harrow-on-the-Hill was almost palpable afterwards.

Later that afternoon, after long stretches walking north from Brentford beside the Grand Union Canal and the River Brent, and almost 20 miles already under my belt, I picnicked in Fryent Country Park with a view of Wembley Arch – feeling like a schoolboy as I opened the tinfoil-wrapped sandwiches Jackie had insisted on stuffing in my bag that morning.

But at times the route was also mentally wearing. For long stretches I felt like I was perpetually walking to catch a bus I was doomed never to take. At one point, because of a diversion, I found myself walking between a narrow set of bollards on the middle of the North Circular Road at rush hour, the smell of exhausts from the ranks of stationary cars almost overcoming me. And the more tired I grew, the more temptation increased around me. Double-deckers with the name of my distant destinations rolled past; black cabs were a wave away, but still I walked on.

My last night was spent in Highgate, north London. I staggered in late, mumbled incoherent hellos and then pitched my tent beside a washing line of clothes, a slide and a deflated football. As I lay down and immediately discovered an infestation of garden snails in my tent, I was painfully aware of my hosts tucked up in a slime-free bed. I wondered if this was quite what I'd intended when I set out. "You sure you don't want to use the spare room?" owner Nick had said to me before going to bed – and I was starting to regret my answer. After all, camping without the wilderness is really just a bad night's sleep.

The following morning I walked through the eerie, overgrown beauty of the Parkland Walk and Abney Park Cemetery and, with the sun in my eyes and dandelion seeds in the air, followed the still algae-green water of the Lee Navigation as it drifted past Walthamstow and Hackney Marshes. I had lunch at The View Tube café just a stone's throw from the Olympic Stadium. Then I followed the elevated Greenway – built along the earthworks containing the Northern Outfall Sewer – for five hard final miles to Beckton Park, where the end of my walk was almost in sight.

As the first glimpses of the River Thames appeared I remembered what Jenny Humphreys, route manager of the Capital Ring, had told me before I left. "Because I've walked the Capital Ring," she said. "I feel like I 'get' London, how it's all sewn together." Now I understood what she meant. I'd been caught on the rim of a wheel spinning round a central axis; I had seen every face of the iconic city skyline. My shoulders and hips ached where the weight of my bag had cut into them, my feet were blistered and bruised, but I felt I understood the sheer scale of London in a way that I had never known before.

Once I'd hopped on and off the Woolwich Ferry (the foot tunnel is closed until August for refurbishment), I was back at my starting point with my adventure complete. Despite the bad nights' sleep, the snails and the awful music from next door, there's something pretty magical about being welcomed into people's private lives – even if it's just as far as their back garden.

For more information on the Capital Ring walking route, see tfl.gov.uk. Audio guides and maps can be downloaded at walklondon.org.uk

For Simon Calder's interview with Aaron Millar and two of his hosts, go to independent.co.uk/gardencamp

Please camp on the grass

Victoria Webbon is the founder of Campinmygarden.com

What's it all about?

Campinmygarden.com is the only online garden camping community in the world. It allows people to advertise their own private gardens as temporary campsite accommodation and book other members' gardens to go camping in.

How did you come up with the idea?

Wimbledon – the tennis tournament. There are loads of beautiful houses and gardens in that area but not that many hotels and B&Bs. I just thought: what a missed opportunity. So I started thinking about other events and places which you might want to visit but you can't find affordable accommodation.

How does it work?

First you need to join as a member. Everybody has their own profile page where they can add their garden and fill in as many details as they want about themselves. It's completely free to use, money is exchanged purely from camper to the garden. The garden owner is in control of everything: they set the price and when they want to offer the gardens. It's up to them if they want to accept or decline a booking. The site itself relies purely on advertising revenue.

What are your hopes for it?

My main hope is that people just enjoy using it. I want people to make friends and feel a part of the campinmygarden community. I want people to feel like they have got friends staying in their back gardens, not strangers.