How DO you flee bears and bison on a bicycle? New father sets off on 16,000 mile bike ride through the wilds of North America after learning he had Alzheimer's at just 39

The wording on the can of bear-repellent didn’t exactly inspire confidence: ‘Use to deter an aggressive or charging animal. The recommended minimum distance between user and bear should be 25ft. Using the spray improperly can have undesirable effects . . . and may actually attract bears.’

‘Brilliant,’ I thought, as I crawled into my nylon one-man tent under the Canadian wilderness sky and pulled my mess tin and Army rations out of the bicycle panniers that were part of my 140kg kit.

This was the equipment I needed to get me round the entire North American continent on two wheels.

I was undertaking this epic, eight-month journey to raise funds for Alzheimer’s research. But it wouldn’t help anyone if I got myself eaten on the first leg, just a few days out from my starting point near Toronto.

This would be my Dementia Adventure, a 16,000-mile circuit of highways and side roads, back streets and cycle paths...

I didn’t dare risk cooking up anything that might attract unwelcome visitors, so I’d have to eat cold scran — a cheese sandwich and a bar of chocolate for me.

This unscheduled stop in the wilds was my own fault. I’d been up since 4am and, after cycling into a headwind that was blowing heavy rain all day, I had decided to ignore the campsite where I’d planned to spend the night. Instead, I’d wanted to see how far I could push on.

It was cavalier, a stupid error — due in part to the general confusion and increasing memory lapses that come with early-onset Alzheimer’s.

I was approaching my 40th birthday in the knowledge that I had only a few good years left. Like my father before me, I was unlikely to see my 45th, thanks to a rare genetic disorder that had also claimed my older brother.

My response was to fight back. After a childhood in care homes, and a 23-year career in the Army — in the Royal Engineers and then the postal and career service as a commando — fighting was second nature to me.

I planned a gargantuan bike-trek across the width of the continent, from the Great Lakes to the Rockies, up to Anchorage in Alaska, then back down again and over the border into the United States.

There, I’d pedal down the west coast to Los Angeles, follow the Mexican border and cross Texas, dip down into Florida to Miami, then head up the east coast to New York and then home — straight through New England back to Ontario.

This would be my Dementia Adventure, a 16,000-mile circuit of highways and side roads, back streets and cycle paths.

To put that in perspective, it’s only 12,500 miles from North to South Pole.

The temperatures were going to range from 125f down to minus-10f. But with my mind already subject to alarming lapses, I couldn’t tackle it without back-up. Luckily, I had the best.

I planned a gargantuan bike-trek across the width of the continent, from the Great Lakes to the Rockies, up to Anchorage in Alaska, then back down again and over the border into the United States (file picture)

My partner, Vicky, was plotting my course from our home near RAF Brize Norton in Oxfordshire, as she followed my signals on the satellite tracker.

She did this in between working as a part-time gardener and carer, studying for a diploma in photography, and looking after her 11-year-old daughter, Katy, and our newborn baby, Dexter. Because of the time difference with North America, Vicky was often up till four in the morning to be my ‘Mission Control’.

I did not doubt that she could do it. Her support has never been less than incredible.

Within 24 hours of finding out that she was unexpectedly pregnant with Dexter, we were told the true severity of the Alzheimer’s sentence hanging over me: I had five to seven years left.

Vicky barely flinched. ‘I’d rather have five minutes of amazing,’ she said, ‘than a lifetime of never having met you.’

Secretly, as we prepared for the ride, I worried that I was being selfish by leaving her on her own for a year, when we had so little time left together.

But it was Vicky who urged me on, pushing me to do it. ‘Go,’ she said, ‘before it’s too late.’

She also forced me to take my limitations seriously, repeatedly warning me to take the vitamin supplements that were prescribed to slow the disease’s progress.

‘Don’t get overtired,’ she kept saying. ‘You know that only makes your symptoms worse. Listen to your body whenever it tells you to take a break. You’ll make a potentially fatal decision if you’re not thinking clearly.’

I’d try to shrug all this off, telling her that other endurance cyclists had tackled similar challenges and made it home in one piece.

Her face would darken: ‘I know, Chris. But none of them have terminal Alzheimer’s.’

That’s fair comment. The sad news, though, is that I’m far from alone. Quite apart from the rare genetic blight that affects my own family, every minute of every hour someone new in the world is diagnosed with some sort of dementia.

One in three of us over the age of 65 will have to learn to live with the disease, two-thirds of them women — who are twice as likely to develop it in their 60s as breast cancer. This represents nothing short of an epidemic.

Alzheimer’s is a ticking timebomb, one of the world’s leading causes of death, and as yet there is no cure.

I aimed to raise at least £40,000 for the Alzheimer’s Research charity. The work they fund will probably be too late to make a difference to my life, but it might just save my two eldest children and baby boy, who are all living under threat of the same fate and too young to be tested for the gene.

Either way, my motto is to take life one day at a time.

I’d never been much of a cyclist, more a general all-rounder who had done the odd sporting event — including one of the biggies, the Mount Everest Marathon.

In fact, the furthest I had ever cycled in a single day was 38 miles — from my home to Cirencester and back — and that was a test-run after I bought the American-made Surly bike I intended to use on my cross-continental travels.

My biggest problem in training was balancing the bike.

One morning in Alberta, I rounded a corner and came face to face with a herd of bison filling my two-lane highway. Larger than cows and with Viking-style horns, these snorting beasts were grazing on the verges

It was laden with a tent, sleeping bag, cooking equipment, ration packs, medical supplies and sundry other kit, including electronics such as the Yellowbrick two-way satellite tracking device as used by round-the-world yachtsmen.

All that weight had to be evenly distributed: any imbalance could pull me over, especially in high winds.

Setting off on my first few training runs with my feet clipped into the pedals, I wobbled like a toddler without stabilisers.

There wasn’t much time for practise before, on April 26 last year, I boarded an Iceland Air flight for Canada.

The ride had to start somewhere, and I’d decided to set off from Brighton, Ontario, just outside Toronto — the home of an old mate, former Sergeant Major Dean Stokes. He’d been my jungle combat instructor, and we’d served together in Sierra Leone: I knew I could rely on him without question.

When we touched down, I phoned him to ask for a lift from the airport along with my bike and more than 10st of kit.

‘I’ve only got a hatchback,’ he protested. But he borrowed a bigger vehicle and agreed to ride alongside me on the first day, for moral support.

Just six miles after we set off, he got a call from his wife Nicole, a medic. She had been ordered to Nepal, to help victims of the recent quake. Dean had no choice — he had to turn round and head home.

‘Chin up, mate,’ he shouted as he cycled off. ‘You’ve only got another 15,994 miles to go!’

I laughed, but inside I was churning with fear.

I was on my own now, and it was up to me to keep to the right track.

In recent months, I’d been finding it increasingly difficult to remember things, and whenever I underwent cognitive tests in hospital, I didn’t fare that well.

At an assessment in London, I was given three words to remember — but by the time I’d got to the third, the first one had flown right out of my mind.

Then the doctor held up photographs, asking me to identify different objects. I named the shovel first time round without difficulty . . . but five minutes later, when the same picture came round, the word had gone right out of my head.

As I pedalled hard, heading east for the distant Rockies, I tried to tell myself it didn’t matter. I’d always been hopeless with directions anyway, and I had my navigational GPS to guide me. What I hadn’t realised until I set off was that constantly glancing down at the sat-nav was not the safest option, and the unit depended on a strong mobile phone signal, which was not always forthcoming in the wilderness.

Getting lost, however, was not the biggest danger.

The real potential killers came looming up in my wing mirrors — 40-ton trucks whose drivers were sitting eight feet or more above the road, playing music or chatting away on their CB radios, barely aware of lesser mortals such as me.

With only a few seconds before they were dangerously close, I had to steer onto the hard shoulder to avoid being blown off-course by their slipstreams.

The Canadian roads were generally in good condition, but the hard shoulders were clogged with salt and gravel after recent snow-clearing work.

This left just a few narrow strips that I could ride on, gripping the handlebars so tightly that my fingers cramped up and my palms were bruised, even through padded gloves. It was like being in a permanent press-up position. My hands got so cold that they went numb and I couldn’t operate the brakes after a while. Whenever I stopped and tried to stretch my fingers, they’d click into position like ratchets.

Each time I wobbled back onto the carriageway to give my hands a break or avoid another mini-iceberg, passing truck drivers would sound their klaxons just as they were about to crush me.

The shock could make me jump right out of my saddle. I ended up with scabby elbows and legs as well as some impressive bruises on my glutei maximi — buttocks to you and me.

The further I travelled from civilisation, the quieter the roads became. I didn’t make any noise myself, so I was able to see much more wildlife than I could have spotted from a car.

Moose, black bears and deer became common sights, though I was glad to be whizzing past them. The biggest bears, the grizzlies, were able to match my top speed, so I’d read, and I had no intention of hanging around to become a meal on wheels.

One morning in Alberta, I rounded a corner and came face to face with a herd of bison filling my two-lane highway. Larger than cows and with Viking-style horns, these snorting beasts were grazing on the verges.

I was right in among them before I knew it. I didn’t want to spook them, so I slowed almost to a standstill as they all looked up.

Quietly, I unclipped my feet from the pedals so that I’d be able to do a runner if I fell off, and carried on moving very slowly, looking right and left all the time.

There were several calves and I tried not to get between them and their mothers. They were all so close I could feel the warmth of their grassy breath.

Increasing my pace a little, I was alarmed to see some were speeding up with me. I went a little bit faster and they started running.

By the time I’d crept up to about five miles an hour they were cantering along with me, their hooves pounding the earth and throwing up great clouds of dust. It was all rather surreal, as if they thought I was one of them.

They ran with me for about 100 yards before they gave up.

Looking back at them with relief, I knew that things could have gone horribly wrong, but in a strange way it was also rather magical.

Not all my encounters were so friendly.

On a road in the middle of nowhere, I’d stopped to have a bite and call Vicky, when I noticed a dark-green pick-up truck approaching slowly in the opposite lane. It pulled up opposite me, and a big guy aged about 45 with straggly black hair and a beard got out. He stood staring at me. The hairs rose on the back of my neck.

I couldn’t saddle up and ride off — it took too long to get that deadweight of equipment rolling.

If this guy proved too much of a danger, if he pulled a gun, for instance, my best hope of getting away from him was to run. But that meant leaving the bike, which was out of the question. So I continued munching my sarnie.

‘Hey man, can you help me with something?’ the guy called out. I tried not to show how frightened I felt. ‘I need to get something out of the back of my truck.’

I put down my sandwich and, in my broadest Manchester accent, yelled back: ‘You what, mate? Why would you stop here in the back of beyond to get me to come over to the back of your truck?’

The guy looked less confident, so I kept shouting: ‘What have you got in there anyway, an alligator? I’m not helping you — do you think I’m stupid?’

Then I stuffed the rest of my sandwich in my mouth and mounted the bike, pushing hard to build up speed. I watched my wing mirrors with my heart pounding for the next half mile, but to my relief I never saw him again.

Most Canadians were far more friendly, and when I told them why I was making this journey many were keen to tell me their own stories about caring for a loved one with dementia.

Some people did more to help me than I could have dared ask — such as Mindy, a truck driver on the Alaska Road.

While heading south outside a town called Coal River, the bike started to make a clanking sound. I limped into a campsite near the Muddy River Indian Reserve, to be told that the nearest bicycle repair shop was in Whitehorse, more than 400 miles away. And the next bus wasn’t for four days.

As I was wondering what to do, a huge two-tanker fuel truck swung into the car park and a woman in her 40s with a mane of black hair climbed down from the cab.

I gave her my cheekiest Mancunian grin and asked whether she was going anywhere near Whitehorse. ‘If you give me a ride, I’m happy to pay something towards the petrol,’ I offered.

That made her laugh, either because she was towing an entire reservoir of fuel or because I’d said ‘petrol’ instead of ‘gas’.

With a shrug, she offered me a lift in the cab and we strapped the bike to the roof of the tanker with elasticated bungee straps. I shared the passenger seat for the next 400 miles with her two bull terriers.

Even with 1,000 gallons of gasoline on board, Mindy drove like there was no tomorrow, and dropped me right outside the repair shop.

Repairs took only an hour or so, and then I was able to load the bike onto a Greyhound bus for the return journey to the Muddy River campsite.

One big meal inside me and I was on the road once more, covering those 400 miles to Whitehorse all over again, this time in the saddle. One of my Army buddies texted to say: ‘It’s downhill all the way to Los Angeles now.’

If only that were true.

Adapted from Five Minutes Of Amazing, by Chris & Vicky Graham with Wendy Holden, published by Sphere on September 22 at £18.99. © Chris Graham 2016. To buy a copy for £15.19 (offer valid until September 10) call 0844 571 0640 or visit www.mailbookshop.co.uk.