In which your reporter starts a 120km circumnavigation of the capital for charity… and the hell of it.

Bar a somewhat underproductive first few months, I’ve been walking all my life. Summer Sundays of my childhood would be spent ambling along towpaths with family members or exploring wildwoods with mates.

Then life happened, and Sundays were for football, or drinking, or parenting, or a combination thereof. But the urge to wander remained. I’d been reading writing about walking — Paul Theroux’s 1982 trip around this island’s perimeter, Simon Armitage’s thoughtful progressions along the Pennine Way and South West Coast Path, Iain Sinclair’s efforts to shadow the M25 in London Orbital.

My journey had also come to its own junction: not so much a crossroads as a roundabout. The girls’ football team I’d been coaching every week for five years had disbanded — a verb more suitable for music, but somehow less apt for the diminuendo of the band I joined in 2006 but which has had one gig in two years and hasn’t recorded a note in four.

With time on my hands and an itch in my feet, I was ready for a new challenge, if not necessarily a time-sapping commitment. Then I noticed a charitable circumnavigation of the capital city: Mencap’s Capital Challenge, a 120km-walk split into quarters on four summer Sundays, serendipitously spread between the end of the football season and the start of a family holiday. Time to put on a different pair of boots.

So it’s up at 6am, the morning after my 44th birthday. (Hangovers haven’t happened for nigh-on six years, and an early night is sometimes not so much a necessity as a treat.) The date seems auspicious, the hour forced by the first quarter of the loop starting the farthest away. But it’s not the first time I’ve tumbled out of bed and pointed myself toward Wembley.

By 6.30am I’m walking eastwards towards the sun and, more achievably, the nearest train station. Fortunate to live in an almost offensively beautiful part of the world, I start the amble on the Thames path, parkland and views almost exclusively mine at this hour.

Outside all is pastoral, but between the ears there’s still that voice. It’s a stupid idea, I’m an old man, it’ll be uncomfortable, beyond my scope, and not that impressive anyway. But one of the reasons to do things like this is to prove to ourselves that we can. I may be out of my comfort zone but I’m hardly hanging off a Himalaya. I’m just going for a walk.

Ten train stations and 13 Tube stops later, it’s into the blazing sunshine at Wembley Park; turning my back on the national stadium’s arch I march uphill past the famous football pub The Torch. On the winding way from station to start, I’m soon in what feels suspiciously like countryside, momentarily finding myself following a small boy returning from an early-morning errand, balancing a loaf of bread on his head, a scene from time immemorial. When he hears my walking boots clodding up behind him he momentarily startles but quickly returns to his murmured monologue, immediately and instinctively assessing the low threat level.

After assembling in the 1970s time capsule of the Wembley Sailing Club for a pre-perambulation porridge, muscular warm-up, obligatory health-and-safety and hearty good-luck wishes, at 9am around 80 of us set out in a broadly easterly fashion and a matching set of pink T-shirts.

Reservoirs have long served a dual purpose, affording us water and leisure, and this is a nice start — an amble alongside a proper lake-like landscape, a valley of the dammed rather than a rectilinear reservoir resembling a glorified kitchen sink. With soul-crushing dullness the local officials call it the Brent Reservoir, but the locals call it Welsh Harp after a nearby pub, whose landlord did much to popularise the area and introduce his mid-19th century patrons to outdoor pursuits — pleasure gardens, sailing, cycle races, greyhounds — as well as a pint.

Not that all is bucolic. The path’s twists flicker in and out of view the new tower blocks which loom over York Park, while the audio contains the usual lower 10% of traffic boom. Twas ever thus: after a brief pas-de-deux with single-lane traffic along a narrow bridge on the winningly-named Cool Oak Lane, we hit the A5 — Watling Street, which has resounded to the slapping of sandals for 30 years short of two millennia.

We cross that and the parallel, newer northwesterly diagonals, the Midlands Main Line and M1 — although you wouldn’t know it from the cheerless visuals afforded by a stubbornly opaque bridge panelled in in two-metre flanks of metal. A pink-shirted young lad Tiggers along, jumping to see over the parapet, wondering aloud “Why aren’t I taller?” Careful what you wish for: further along to the south, mercifully unseen, bulks the mass of Brent Cross shopping centre.

Under the A41 and over the Northern Line and you’re in Hendon Park, red London buses pootling along the top of its gentle northerly incline. Not a bad thing to have, a gentle northerly incline: it gives a sunny aspect. The local walking his dog enquires what we’re doing. “Twenty-mile walk?” he repeats, raising his eyebrows and his dog’s hopes.

Soon we hit the North Circular, which will jockey with us for the next mile, and the first evidence of the local Jewish population, which will last a while longer. The first wide-brimmed hat appears just after Hendon Park and as we skirt the northern edges of Golders Green there’s plenty of evidence of the sons and daughters of Abraham, going about their Sabbath business and pleasure with impeccable dress and manner.

Running between the competing charms of Dollis Brook and the A406, Brent Park — named for the river rather than the council — is an unexpected pleasure. In a strip barely 100m wide which could easily be laid waste by its proximity to one of London’s busiest roads, there’s a (reasonably) quiet sunken escape. Mallards, moorhens and tufted ducks like it, and so do I.

The peace can’t last, and after tunnelling under the North Circular the path is temporarily closed for upgrades so we’re forced along our old friend the A406. Broadcasting stalwart Denis Norden once revealed that the only life advice his father passed on was “never take the North Circular”. I’m not sure if the senior Norden was a rambler, but it’s a fair bet that he wouldn’t have enjoyed tiptoeing along the roadside path, strewn with the usual highway detritus: crisp packets, an occasional wing mirror, the scratched-up scree of stones and glass. Stalled in stationary traffic under a broiling sun, a high-performance car farts powerfully; a few spaces back, some character leans pointlessly on his horn, an idiot’s answer to everything.

It’s with gratitude that we leave the A406 for the Dollis Valley Greenwalk — a Dollis parting, if you will — and sink back into the peaceful riverside path which follows Mutton Brook for a next mile or so, emerging briefly into the quietly dignified housing of Hampstead Garden Suburb, where the lamp-post flyers are for an Oscar Wilde production.

All suburbs are planned, but some more so (and by wiser minds) than others. Hampstead Garden Suburb was promoted by Dame Henrietta Barnett, a Clapham lass who used her inherited oil money in various altruistic ways — sending slum kids for country breaks, rehoming workhouse girls, educating the poor, and engaging architects Raymond Unwin and Edward Lutyens to design this suburb, determinedly pluralistic in both architecture and intended inhabitants. It never reached full fruition and market forces have had their way since: just as I’m noting that the high quality of cars in the drives suggest the locals are hardly down-at-heel, a Range Rover owner struggles for a full minute inching his mobile status symbol through a 6’6” traffic-calmer.

By now it’s 10am and Londoners are at their leisure, taking advantage of the options on offer. At Lyttleton Fields, there’s cross-training equipment, the Bishopswood bowls club (“Come and try! Free coaching!”) and tennis coaching aplenty, ranging from seriously-sunglassed professionals of pompous bearing to the mum chuckling indulgently at her son’s fluffed forehand.

Saturdays can be formal occasions too and the Hampstead Garden Suburb Synagogue — built in 1956, a restrained red-brick affair despite its classical stone portico — is busy, smiling elders bending gently to speak to smartly-frocked grand-daughters. Perhaps they’ve just finished the Shacharit morning prayers, or perhaps there’s another gathering in mind: it’s certainly wedding weather, although under traditional Jewish law any happy couples would have to wait until sundown on this sabbath.

As we climb towards East Finchley, the housing stock is agreeably 1930s: Deco design touches, a nice Bauhaus simplicity to the line — suburbia without the sprawl. For all its evocativeness, you suspect some of the Jewish residents wouldn’t be so keen to return to a decade which illustrated as well as any that humankind is capable of aesthetic beauty and godless horror.

Coming up next: into the ancient woodland…

The Mencap Capital Challenge is a charity walk circling London in four quarters, each roughly 30km. You can donate or sponsor the writer at justgiving.com/garyparkinson1974. You can also join in: the East quarter (Royal Albert Docks to Crystal Palace) will take place on Sat 26 May, the South quarter (Crystal Palace to Richmond) on Sat 9 June, the West quarter (Richmond to Hendon) on Sat 7 July.

NORTHERN QUARTER, SAT 5 MAY 2018
• Pt1: Wembley to East Finchley • Pt2: …to Finsbury Park
• Pt3: …to Clissold Park • Pt4: …to Springfield Park
• Pt5: …to Hackney Wick • Pt6: …to Bow Back River
• Pt7: …to Channelsea River • Pt8: …to Royal Victoria Dock

EASTERN QUARTER, SAT 26 MAY 2018
• Pt9: Victoria Dock to North Woolwich Pier • Pt10: …to Maryon Park
• Pt11: …to Hornfair Park • Pt12: …to Oxleas Wood
• Pt13: …to Eltham Palace • Pt14: …to Grove Park
• Pt15: …to Beckenham Place Park • Pt16: …to Penge
• Pt17: …to Crystal Palace Park • Pt18: …to Upper Norwood

SOUTHERN QUARTER, SAT 9 JUN 2018
• Pt19: Crystal Palace to Beulah Hill • Pt20: …to Streatham Common
• Pt21: …to Tooting Bec • Pt22: …to Wandsworth Common
• Pt23: …to Wimbledon Park • Pt24: …to Richmond Bridge

WESTERN QUARTER, SAT 7 JUL 2018
• Pt25: Richmond Bridge to Isleworth • Pt26: …to Hanwell Locks
• Pt27: …to Horsenden Hill • Pt28: …to Sudbury Hill
• Pt29: …to Wembley, and that's that