Tom Dumoulin lead slashed after toilet break as Vincenzo Nibali wins Stage 16

Nibali became the first Italian stage winner of the 100th edition of the Giro after beating Spaniard Mikel Landa in a two-way sprint in Bormio – but all eyes were on Dumoulin, whose overall lead was slashed to 31 seconds after an enforced comfort break ahead of the third and final climb.

Dumoulin, of Team Sunweb, rallied on the Umbrailpass in Switzerland, picking off stragglers one by one, en route to crossing the summit just over two minutes down on his big rivals.

An attack by Bahrain Merida’s Nibali on the descent saw the defending champion drop Colombia’s Nairo Quintana (Movistar) and catch lone leader Landa (Team Sky) as the race dropped back into Italy ahead of the finish.

Nibali ended the host nation’s drought – and revived his chances of defending his crown – by pipping Landa, the new maglia azzurra, to the line after almost six-and-a-half hours in the saddle.

Quintana took third place, 12 seconds in arrears, and ahead of Italy’s Domenico Pozzovivo (Ag2R-La Mondiale), Russia’s Ilnur Zakarin (Katusha-Alpecin) and Italian youngster Davide Formolo (Cannondale-Drapac). Bauke Mollema (Trek-Segafredo) led a chasing group home alongside Bob Jungels (Quick-Step Floors), Adam Yates (Orica-Scott) and Thibaut Pinot (FDJ) before Dumoulin, digging deep, came home to limit his loses to 2:10 over his nearest rival, Quintana.

While Quintana moved within 31 seconds of the race summit, Nibali also rose to third place at 1:12 after a day of drama in the high Alps.

Once the dust settled on the new time gaps at the top of the standings, the main talking point quickly surrounded the reaction to Dumoulin’s unscheduled toilet break inside the final 35km of the race. With the likes of Nibali, Quintana and Zakarin all raising the tempo while Dumoulin struggled behind, questions were asked whether the riders broke the unwritten rules of cycling by failing to afford the pink jersey the respect it deserved.

Billed as the queen stage of the race, the 222km stage from Rovetta to Bormio featured the fearsome Passo del Mortirolo and an unprecedented dual ascent of the legendary Stelvio.

A large break formed after a fast flat opening quarter of the race before Spaniard Luis Leon Sanchez crested the summit of the "easy" side of the Mortirolo to pick up the Cima Scarponi in memory of his late Astana team-mate Michele Scarponi, the Italian veteran who was killed last month after a training accident.

Sanchez’s prize followed a superb gesture of goodwill from compatriot Omar Fraile of Dimension Data, who put his maglia azzurra ambitions aside to let the Astana rider do Scarponi’s memory proud. It was a showing of fairplay that many felt was not replicated later in the stage.

Landa, whose own GC hopes were ended in Stage 9 following the controversial crash involving the police motorcycle at the foot of Blockhaus, was the last man standing from a large break of 26 riders which formed on the Mortirolo.

The Basque climber crested the summit of the Passo dello Stelvio – the second of three climbs – in pole position to take the famous Cima Coppi over the highest point of the race. Although he would miss out on the stage win, Landa moved to the top of the mountains classification for his efforts.

Landa’s near-win almost capped a superb day for Team Sky, who showed their tactical nous by placing three riders – Vasil Kiryienka, Philip Deignan and Sebastian Henao – inside the break alongside the Spaniard.

Movistar, too, seemed to hold all the aces in the GC battle after Andrey Amador and Winner Anacona rode into the leading group of six riders ahead of the final climb alongside Steven Kruijswijk (LottoNL-Jumbo) Jan Hirt (CCC Sprandi Polkowice), Igor Anton (Dimension Data) and Landa.

Landa and Amador had ridden clear on the technical decent on the northern side of the Stelvio – complete with the famous 48 hairpins – before being rejoined by the other escapees with a lead of just under two minutes by the time the race entered Switzerland to tackle the Umbrailpass – the third, lesser-known ascent of the Stelvio.

As the main pack of favourites approached the climb at a fast tempo, Dumoulin suddenly swung to the side of the road before removing his helmet and jersey, before frantically pulling down his bib shorts in a ditch.

Once Dumoulin rejoined the race, the 26-year-old benefited by some pace-setting by Sunweb team-mate Laurens ten Dam – who had been part of the initial break – before setting off on his lone quest to reduce his deficit.

Meanwhile, ahead, Zakarin forced a selection after a controversial attack – leading to a reaction from Quintana, who by now had been rejoined by his Movistar team-mate Amador. Nibali, too, attacked while Dumoulin was down – primarily through the pace-setting of veteran team-mate Franco Pellizotti.

Up the road, Landa dropped his remaining escapees as he neared the summit of a climb being used for the first time in the Giro. Both Kruijswijk and Hirt were caught and passed before the summit, by which point the entire main field had splintered.

While Nibali caught Landa on the descent and Quintana edged clear of Pozzovivo and Zakarin, Dumoulin kept his cool – and although his deficit stretched to three minutes at one point, the Dutchman did enough to keep the maglia rosa for at least another day.

After a masterful, not to say hair-raising, descent, Nibali won the sprint for the stage after Landa overcooked the final bend and gave his rival the best line to the finish – the Basque climber slamming his handlebars in frustration after his rookie error.

Where to start? Certainly, not the big-name favourites who used their rival’s misfortune as a moment to rub his face in the dirt and create a real stink. Having been at the receiving end of Dumoulin’s good faith after crashing in Stage 15, Quintana particularly may regret his actions – although he will say he was merely reacting to accelerations from Zakarin and Nibali, the man who gained most from Dumoulin’s disaster.

On the other side of the coin, Fraile’s gesture to allow Sanchez to take the points over the Mortirolo in memory of Michele Scarponi deserves praise – and it’s worth mentioning that Landa, too, was part of this goodwill. That Landa went on to crest the next two summits in pole position – picking up the prestigious Cima Coppi and maglia azzurra in the process – sees the Spaniard crowned the day’s Giro Hero, even if he was ultimately denied by Nibali, who saved Italy’s blushes with a belated win that has blown this race apart.

Tom Dumoulin didn't mince his words when explaining on live TV just what went wrong before the Umbrailpass: “I needed to take a dump. I couldn’t hold it anymore. On the first time of the Stelvio I started to feel it on the downhill, and I just had to stop – it was not possible to continue anymore."

Asked how he felt after his problem, Dumoulin said: “How did you think I felt? I decided to fight and fight and fight, and then take conclusions afterwards. That’s what I did, and I think that’s good. But I’m very disappointed with the day, also. Right now, I’m just disappointed because I think I was one of the strongest today.”

The Dutchman later told Eurosport’s Juan Antonio Flecha: “I had good legs but if you have a problem like this there’s nothing you can do. The race goes on at that moment. I have a good downhill, especially when I’m focused, but I didn’t drink enough after my problem, so pedalling was hard. I lost a lot of time unnecessarily today.”

Three categorised climbs – but nothing like the monsters the riders had to tackle on Tuesday. Stage 17 from Tirano to Canazei, though, is not to be taken lightly: 219km long and featuring the climbs of Aprica and Tonale, it’s a draining day for Dumoulin et al and culminates with a long uphill false flat.