You hear the thump of helicopter blades first.
Car horns, cowbells and vuvuzelas lift the volume to ear-splitting levels. Police sirens wail and hundreds of Norwegians start chanting, "Heia! Heia!"
The leaders emerge through a tunnel of fans who step aside, matador-style, at the last possible moment. In the blink of an eye, the riders are gone. Soon the next group appears and the wall of noise rises to another crescendo, urging the straining competitors upwards and onwards.
The Tour de France is more than a bicycle race. It's a three-week endurance test that demands dedication, stamina and meticulous planning. A head for heights is crucial, as is the importance of taking the right kind of "liquids" on board. And that's just the spectators.
Way back in the mists of pre-Olympics time, 198 sinewy cyclists started this year's edition of the legendary contest. They battled on a daily basis for the privilege of wearing the maillot jaune; the yellow jersey, which denotes the overall leader. Specialists fought for the right to don green, white and polka-dot jerseys, which are for the points leader, best young rider and king of the mountains, respectively.
By the time those still in the saddle glided along the Champs Élysées in Paris, they had pedalled 3,497 kilometres over three gruelling weeks. They had criss-crossed the Alps and the Pyrenees in a punishing schedule that sapped strength and tested sanity.
TO GRASP THE FINER points of the spectacle, I've undergone a Tour de France crash course. I've read up on the favourites, studied maps of the stages and immersed myself in the folklore and traditions that are part of any great sporting event.
I now know my peloton (main group) from my poursuivants (chasers). I've learned that domestiques, or servants, work unselfishly to help the team leader and that a musette is a feed bag handed over at the roadside.
I own a bike but I wouldn't call myself a cyclist. My rusty steed carries me to Mui Wo ferry pier in time for the 8.05am boat to Central but that's about it. The only peloton I'm familiar with is the one that forms when commuters bunch together on leaving the pier to head home.
I've picked up most of what I know about the Tour de France on a bar stool in Wan Chai, of all places. A few years ago, I asked Jonny Porteus, manager of the White Stag pub, what on earth he was showing on television that could be more important than Premier League football.
"Women's Tour of Flanders," came the reply.
On evenings throughout July, the pub fills with cycling fans who are every bit as knowledgeable as those screaming at the side of French roads. Regulars are happy to enlighten novices and there are usually well-thumbed Tour de France magazines on the bar.
There's a saying that the only way to appreciate the high drama of Le Tour is to watch on TV. It's also fair to say that the only way to experience the event is to select a stage, pack a picnic and wait for the parade to arrive.
Watching the cyclists whiz through a town or village is one thing but as any tour veteran will tell you: "it's all about the mountains". On flat stretches, the peloton comes and goes in a "blink and you miss it" blur. It makes a lot more sense to find a spot on the sharpest incline of the steepest peak, where the competitors will be going relatively slowly and are likely to be spread over a larger distance. This turns out to be easier said than done.
Attempting to find out in advance when the mountain roads are due to close is futile. Official times are posted weeks beforehand but in reality, the gendarmerie (French national police) make ad-hoc decisions based on the number of vehicles already squeezed onto a summit.
In the village of Lochieu, in the Massif du Jura, you get the impression the inhabitants could do without all the commotion. Tractors rather than bicycles are the transport of choice in these parts and pre-dawn interlopers are treated with suspicion.
" Fermé," a farmer warns, his jaw jutting out, daring me to disagree. My schoolboy French decodes the follow-up: "The roads closed last night. You'll have to park here and watch."
The route up to the Col du Grand Colombier turns out to be open. At first. A few kilometres into the foothills, however, just as I'm celebrating my good fortune, the outstretched palm of a policeman stops me in my tracks.
"Fool," he yells.
As I'm wondering if I've driven halfway up the wrong mountain, I realise he means the summit is already full.
It's another 11 kilometres to the pass but access is restricted to cyclists and pedestrians. The hike would be tiring enough on the flat but the road looms up like a wall. A cunning plan to hitch a lift up in a municipal truck delivering traffic cones is foiled by the jobsworth gendarme.
"They're not insured to take passengers," he warns.
It's 5.30am and the way ahead is crowded with people of all ages pacing purposely upwards, each with a baguette peeping out of their daypack. Motorhomes draped in national flags are parked in every clearing. Despite the early hour, campers are up and about, coffee mugs in hand. Huge banners, inflatable mascots and photographic equipment are laid out in readiness yet the riders aren't expected to pass through until 4pm.
Halfway up, an encampment of English fans are tucking into breakfast at a table set with Union flag plates, cups and napkins. There's even a string of bunting hanging from the trees.
"They're left over from the queen's [diamond] jubilee. Might as well use them all up," says a wiry man in a Sky Pro Cycling shirt.
Russell and his wife have borrowed his company van for two weeks and are sleeping in the back.
"We do two nights in the van and the third on a campsite. Everyone needs a shower every so often don't they? Would you like a coffee?"
The couple have a substantial back catalogue of Tour stories. Four years ago, in the Loire, they invited two gendarmes to join them for a few glasses of wine. The police officers ended up allowing the inebriated pair to spend a night in the cells as every hotel in town was full. Last year, they found themselves at a campsite party hosted by a group of Australians celebrating victory for their man, Cadel Evans.
"We were all still going the next morning," Russell recalls with a grin.
The anecdotes reveal part of the attraction of following La Grande Boucle, or Big Loop, as the tour is known. Sure, the riders come and go in no time but the parties and camaraderie last a lot longer.
The summit of Col du Grand Colombier is swarming with campers and campervanners; amateur cyclists and unicyclists. The atmosphere is vaguely reminiscent of the Hong Kong Rugby Sevens. There's a pantomime horse, two Danes on rollerblades, a Belgian on stilts and a Frenchman who says he walked all the way up on his hands.
Hundreds of motorhomes are parked bumper to bumper. A Dutch couple tell me they grabbed their prime roadside spot three days ago.
"It's impossible to see each stage," they say. "So we try for a grandstand position as often as possible."
Like the Brits further down the mountain, the pair, clad in orange from head to toe, don't see themselves as obsessive fans but as merely incorporating the event into their summer holiday.
"We've been hiking in the mountains; we picnic by lakes and explore lots of beautiful towns and cities. If you follow the tour, you get to see the best of France and every so often a bunch of cyclists pedal past."
The roads have been closed to vehicles for 10 hours but at 3pm, people in garish figure-hugging outfits are still arriving. Just below the summit I settle on a steep section of road that is hard to walk up. It's crammed with a multinational mix of youngsters, mamils (middle-aged men in Lycra) and their equally enthusiastic partners.
Besides the French, there are devotees from other traditional cycling nations such as Belgium, the Netherlands and Spain here. Australians are out in force to cheer Evans while the Brits line the roadside hoping Bradley Wiggins will become the first of their kind to win the Tour de France. Then there are the Norwegians.
No one is quite sure why there are more Norwegians on a French mountaintop than all the rest of us put together. They don't seem to know either.
"I guess it's because we love cycling," comes the rather feeble explanation from a woman in national costume. "And we're here for 'Eddy Boss' of course."
Edvald Boasson Hagen is part-Norwegian road racer, part-demigod. Around us there are cardboard cutouts of the Team Sky member and his name is painted in bold font across the tarmac. If he struggles up the incline, his compatriots will probably pull him up with mere force of will.
At 3.30pm, the publicity caravan - a convoy of corporate carnival floats - manoeuvres its way up the switchbacks, triggering scenes of delirium. Dance music booms and PR staff hurl sweets and free samples into the throng, who scramble over each other to grab the goodies.
The procession lasts for 45 minutes and the excitable Norwegians cheer everything that moves. They offer high-fives to bemused emergency services personnel and even shriek their approval as a decorated truck promoting ophthalmic products trundles past.
The road is already more obstacle-strewn than an Indian highway when a cow ambles onto the tarmac. Then the monotonous throb of helicopter blades fills the air.
After an eternity spent waiting on a mountaintop, a surge of adrenaline rushes through the crowd, who have worked themselves into an evangelical convention-style frenzy. Like a vision, the first riders appear. The faithful lean forward until there is barely enough room for the leading trio to pass. A Russian, who started on the beer at breakfast, lurches alongside a rider from the BMC team for a few dizzy metres before his legs give way.
We're pushed back by police motorcyclists as the poursuivants sweep past. The shrill cacophony of clanging cowbells, whistles and general hysteria reaches new heights as Boasson Hagen bursts into view.
In the pandemonium, a yellow jersey flashes by. A thousand cameras set to paparazzi mode click away in the hope of capturing a sharp image of Wiggins.
Forty minutes later, the cyclists bringing up the rear pedal past. They're followed by a truck bearing a sign that reads "Fin de la Course". The travelling circus moves inexorably on.
Traffic jams instantly materialise and many drivers wait to let the congestion ease. Others have no choice. After a day putting away copious amounts of alcohol, they would be insane to take on the kind of narrow mountain roads that inspire James Bond car chases.
With an hour or so to kill, I return to my Tour de France reading.
The largest free-to-watch sporting event on Earth first took place in 1903, when a journalist at a French sports daily devised a bicycle race around the perimeter of the country in a bid to drum up publicity for his newspaper. Riders on heavy machines endured stages of up to 471 kilometres in one go, often cycling long into the night. They made all their own repairs and even had to organise their own food and drink. The contest captured the nation's imagination and huge crowds gathered to cheer the winner back to Paris. The Tour de France was born.
Changes to the rules and technological innovations have continued ever since. A mountain stage was first introduced in 1905 and since 1913 the route has alternated each year between a clockwise and anti-clockwise circuit of France.
The yellow jersey, chosen to reflect the colour of the sponsor's livery, appeared in 1919. Gears were finally allowed in 1937 and meant that riders no longer needed to change their rear wheel each time they began an ascent.
The race has long served as an extended promotional video for the French Tourist Board. Carefully choreographed helicopter footage combines the sporting action with lingering shots of sunflower fields and chateaux, mountains and lakes. You may catch sight of a donkey kitted out in a yellow jersey but don't expect to see the peloton pedalling past an industrial estate too often.
Each year, organisers receive about 200 requests to host a stage of the tour, which costs between €55,000 (HK$525,000) and €90,000. As soon as a town is selected, local dignitaries begin planning how to best utilise their fleeting moments of primetime coverage. Most do a commendable job of creating a carnival atmosphere for locals and the thousands of visitors who stop by.
ALBERTVILLE, IN THE department of Savoie, proclaims itself a Mecca for cyclists and proves it by boasting more bike shops than boulangeries (bakeries). The town knows how to put on a show, having hosted the 1992 Winter Olympics, and is the starting point for today's stage.
The scenery en route from my overnight lodging in nearby Annecy is quintessential Switzerland, which is not surprising as the Swiss border is just 35 kilometres away. Through the inky pre-dawn light, it's possible to make out wooden chalets nestling in steep valleys. Snowcapped alpine peaks soar above picturesque Lake Annecy. I'd like to linger but I've got a mountain to climb.
Signs warn that the road up to Col de la Madeleine is due to close at 11am. It's now 5am but I'm not taking any chances. The hire car labours up successive switchbacks and seems happiest in first gear. A now-familiar line of motorhomes are parked in every available space and several tents are pitched on precariously narrow ledges.
I press onwards through banks of thick cloud as the summit nears. Even at this ungodly hour, parking places are non-existent until some bleary-eyed Czechs make room. As the sun moves higher, the clouds disintegrate, revealing valleys and villages far below. France is all set to look drop-dead gorgeous in time for its worldwide TV audience.
I recognise a few faces in the crowded mountaintop cafe. All have the dishevelled appearance of people who would rather be asleep at such an hour. We swap snippets of race gossip over mugs of heart-starting coffee. Only another 10 hours to go.
There aren't as many Norwegians today. Word filters through that they're massing on Col de la Croix de Fer, the second peak of today's stage. There's still a festive atmosphere when the publicity caravan eventually comes thudding by. Once again, the spectators cheer wildly as a succession of conglomerates present themselves in as benign a light as possible.
We're showered with sachets of washing powder from France's largest detergent company and biscuits from a well-known bakery. Fortunately, representatives from the nation's No1 manufacturer of disposable razors choose not to fling their products into the howling crowds.
We know the leading group is getting nearer when a squadron of nine helicopters swoops past. Apparently, seven are carrying celebrity sightseers and the other two are responsible for beaming moving images to a worldwide audience.
For a bicycle race, the carbon footprint of the Tour de France is enormous. Besides the airborne entourage there are 4,500 support staff in 1,500 vehicles, though this number pales in comparison to the thousands of cars, motorbikes and campervans that zig-zag across France for three weeks. Formula One motor racing chiefs claim their sport is less polluting.
As the riders approach the summit via a series of savage switchbacks, one of the choppers roars up from beneath our feet and hovers a few metres overhead Apocalypse Now-style. The riders come around the bend and the adrenaline is back; coursing through the spectators like electricity.
The leaders, peloton and stragglers all make it up and over the summit within half an hour and without incident. The road reopens and traffic builds as teetotallers and designated drivers make a dash for campsites, hotels and supermarkets.
After only two days, the early starts are taking their toll. I'm tired, hungry and not sure whether I have the stamina to continue. By contrast, race leader (and eventual winner) Wiggins appears on TV to say he is feeling great and is ready to step up a gear during tomorrow's 226-kilometre stage; the longest of this year's Tour.
It's a new day and I need to step up a gear as well. I've "overslept" but, reassuringly, police notices in the picture-postcard alpine town of La Chambre confirm that the mountain road to Col du Grand Cucheron won't close until 9.40am. It's only 5.50am but at the first intersection I'm confronted by the familiar sight of a gendarme shaking his head and uttering the dreaded F word: " Fermé."
Back in the town centre there are cops on every corner. Walkie-talkies crackle and helicopters buzz like mosquitoes overhead. La Chambre is under lockdown. If you didn't know that the world's most famous bicycle race was coming through, it would be reasonable to assume a crazed gunman was on the loose.
The route is as flat as a pancake and the riders zip past us in less than 15 seconds. Within minutes, the roads reopen. Spectators start packing away picnics and folding up flags. Local entrepreneurs dismantle their temporary refreshment stalls for another year. After the anticipation and excitement of the mountain stages, it all feels like an anticlimax.
Keeping up with the Tour de France has been an energy-sapping logistical challenge. The rewards outweigh the effort involved in getting to the right place at the right time. But only just.
Next year marks the centenary edition of the great race but to follow it non-stop for three weeks you'd have to be slightly mad. Or Norwegian.