If I have to pinpoint the exact moment I realise things have got serious, this would be it. I’m sitting at a table in the restaurant of the Chia Laguna Resort, on the south coast of the Italian island of Sardinia, accompanied by a bottle of beer and a plate piled so high with food that it’s threatening to keel over and dispense a mixture of pasta, meat, fish, salad and more meat onto my lap.

I’m quietly pleased with myself – quiet because I’m on a table for one, and pleased because I’ve just raided the buffet with all the restraint and finesse of a child let loose in the Woolworths pick-and-mix section, and I’m about to shovel it all, very quickly, into my gob.

But then I look up and around, and in the few minutes since I sat down with the fruits of my buffet raid (which contains no actual fruit, obviously) the room has filled with people, none of whom have beer or mountainous plates in front of them; many of whom are wearing branded sportswear and caps (indoors! imagine!); and all of whom have the wiry, muscular look of proper athletes.

This is, unmistakably, a room full of function – food, clothes and bodies designed to do things (like fuel, or wick moisture, or run) rather than be things (like fashionable, lumpy or tasty). I shouldn’t be surprised, I suppose, because in two days almost everyone staying in the resort on this balmy Thursday evening in April will compete in the Chia Laguna Half Triathlon, which is roughly twice the distance of a standard, Olympic-distance triathlon – or, to put it another way, half the distance of an Ironman.

I’m racing, too, though I’ve drafted in my brother-in-law, Ross, to share the load – by which I mean he’ll take on the 1.9km sea swim, before handing over to me for the 90km bike leg, and he’ll then run the 21km half-marathon distance to the finish.

As my sister put it a few weeks ago: “I can’t help thinking Ross drew the short straw here…” At this point, though, Ross is still in the UK, so it’s left for me to scope out the opposition and recce the course – and by “recce the course” I mean wander down to the beach and go for a quick swim, then cycle down the road for a bit to make sure I’ve managed to put my bike together properly after flying it over in bits.

Other than a lone seagull it's just me and a vast sandy beach

Chia is at the southernmost tip of the island, about an hour’s drive from the Sardinian capital, Cagliari, and it sits just back from the coast, separated from the sea by a lagoon with its own population of flamingos. It’s a short walk from my room to the beach, skirting the edge of the lagoon, and the scene that slowly emerges through the scrubby clumps of bushes is genuinely stunning.

Other than a lone seagull, it’s just me, a vast stretch of white sand extending east towards a tower-topped headland, and ice-blue water lapping and fizzing gently at the shore. This isn’t the point at which Ross will start the race the following day – to get to that I follow a narrow path that winds west along the coastline past a rocky outcrop, until I’m spat out at a small beach where barriers are being put up and a few people in wetsuits are testing out the water.

I have a quick dip (this is April, so it’s freezing) then head back to pick up my bike. The wind – as it’s apparently inclined to do round these parts – is whipping along the coastal road, while the mid-afternoon sun beats down on the tarmac. I follow the road west for a few winding, undulating kilometres before turning back, which is just far enough for me to get some idea of what we’ll be in for tomorrow.

When Ross arrives later that afternoon, we have just enough time to scope out the beach and drop my bike off in transition (that’s the area in a triathlon where competitors change between disciplines) so it’s ready for the start the following morning – even if the two of us aren’t. Race Day It’s an early start and, after loading up on breakfast, we wander down to the beach, where the other competitors are beginning to gather for the start of the 1.9km swim around a course marked out by buoys.

There’s barely a cloud in the sky, though it’s not yet warm and the wind has now turned yesterday’s glassy pool into a wild and wavy mess of bluey green foam. As the first group of athletes sets off – those like us who are doing the race as a relay are in the last group to go – we watch as the waves and a fearsomely strong current pull them out of line on the charge to the first buoy.

Ross, now wetsuited up and waiting to be called to the start line, looks back at me with the wry grin of a condemned man. I stick around for a few minutes and watch him battle through the first few sets of waves, before I squeeze through the small crowd of spectators and find my bike in the transition zone. It’s conspicuous for being a regular road bike – most others are aero-efficient monsters that, like their owners, are purpose-built to go fast – and I loiter alongside it while the lead athletes stream out of the water, squeeze out of their wetsuits, grab their bikes from the rack and set out on the bike leg.

When Ross arrives he looks remarkably fresh (which is no small piece of luck, considering he’s still got a half marathon to run). He peels off the timing chip around his ankle and I strap it onto my own leg before haring out of transition and hopping onto the bike. My route is a classic out-and-back – it snakes along the hills overlooking the Tyrrhenian Sea before cutting inland, reaching the turnaround point, and then retracing the same roads back to transition.

It’s not exactly a conventional or a particularly relaxing way to see this part of the island, but it’s impossible not to be seduced by the epic coastal scenery. As lush hills and cliffs rise up from the turquoise sea, the road traces it – which means steep climbs that etch their way up wind-battered peaks before plunging down the other side.

It’s hard work – and god knows it would be harder if I’d just done a 2km sea swim – but whizzing (or wheezing) past small harbour towns, and beaches that look like they’ve been stolen from the Caribbean and dropped into the Mediterranean, softens the blow.

Once the route dives away from the coast things start to flatten out, and the sun that’s been gently bathing the landscape (and me) is beginning to warm things up a bit. I’m making good progress, though – passing some, being passed by others, trying to remember to throw the odd energy bar or gel into my fuel tank/mouth – and my legs feel surprisingly good.

My legs start feeling wobbly just as the steep climbs loom

When I reach the turnaround point at Porto Pino, a little under an hour and half in, I’m actually looking forward to the second half of the ride and start identifying ‘targets’ to overtake further up the road ahead of me, which is all well and good until my legs suddenly start feeling wobbly, just as those steep climbs from the way out begin to loom on the horizon.

I’ve ridden much further than this plenty of times before, but rarely have I ridden as fast as I can for more than 50 miles without pulling over for cake and a strong coffee at least once. It hurts. A lot. Not as much, it turns out, as running a half marathon in the baking, late-morning Sardinian sun. I hand over to Ross in transition and he’s looking relaxed, having spent the past couple of hours chilling out in the hotel.

Next time I see him, he’s making a decent pace but throwing cold water over himself and puffing out his cheeks. In fairness, he’s far from alone – there are some ragged-looking bodies out there by this point – but the crowds that have assembled to cheer on the competitors are doing their best to pull people around the course.

Finally – five hours and 40 minutes after we set off, and more than an hour and a half after the winner rolled in – Ross crosses the finish line and I saunter over just in time to sheepishly grab my finisher’s medal. It’s hard not to feel a little guilty – after all, not only did I share the burden with someone else, but all I had to do was ride my bike along one of the most eye-poppingly gorgeous bits of coastline in Europe.

Still, you’ll have to prise that medal out of my cold, dead hands. Maybe I’ll be back this year to do the whole shebang. Or maybe I’ll find some other mug to rope into it – which shouldn’t prove too tricky: tons of Italian food, balmy spring weather, breathtakingly pretty beaches, and just a little bit of temporary pain. What’s not to like about that?

Travel Details

The 2017 Chia Sardinia Triathlon 70.3 takes place on 23 April. Citalia has a seven-night trip to Sardinia, staying at the Chia Laguna Resort on a half-board basis from £835 per person – saving £386 per couple. The price includes seven nights in a Classic Cottage at the Hotel Village, return flights from London Stansted with easyJet. Based on departures 22 April 2017. For more info or to book: 012 9376 5066; citalia.com. Early bird race entry is €195 before 26 February. followyourpassion.it