Jelle Wallays (Lotto Soudal) won stage 18 of the Vuelta a España following a breathless finale in Lleida that saw him out-sprint breakaway companion Sven Erik Bystrom (UAE Team Emirates) just as the peloton was bearing down upon them in the finishing straight.

Peter Sagan (Bora-Hansgrohe) opted to open his sprint from a distance in a desperate attempt to catch the escapees, but although the world champion's effort was a prodigious one, he had to settle for third place on the same time as Wallays. Elia Viviani (Quick-Step Floors) placed 4th ahead of Ivan Garcia (Bahrain-Merida).

On a transitional day that was expected to peter out into a bunch sprint, Wallays, Bystrom and fellow escapee Jetse Bol (Burgos-BH) – who was dropped from the break with 7km to go – defied all expectations to pull off a remarkable heist in Catalonia. The trio escaped after just 3km, and their advantage was never allowed to stretch beyond 2:30, but they took advantage of a brisk tailwind to summon up the wherewithal to fend off the bunch on the run-in.

"I think everyone was expecting a mass sprint, but I had a crash after the first rest day, and I had something in my mind to do something in a stage, and one of them was this stage," Wallays said afterwards. "Everyone expected a mass sprint, but I know if I'm good I can surprise many riders, and today I did it."

Simon Yates (Mitchelton-Scott) retains the overall lead with an advantage of 25 seconds over Alejandro Valverde (Movistar). The red jersey was prominent at the head of the peloton in the closing kilometres, mindful, perhaps, that Valverde might try to claim bonus seconds at the finish. Instead, the general classification picture remains untouched ahead of the Vuelta's grand finale in the Pyrenees on Friday and Saturday.

"It was OK until the final, it was really fast because of the wind," Yates said. "It was a hard final, but the rest was a nice day. I'm looking forward to tomorrow now."

Thursday belonged to Wallays, however, and the Belgian has previous experience when it comes to defying the sprinters and out-manoeuvring a breakaway companion in a major race. In 2014, Wallays cannily denied Thomas Voeckler in a two-up sprint to win Paris-Tours, while the following spring, he won Dwars door Vlaanderen after clipping away from the winning move in the finale.

As the kilometres ticked down towards Lleida, Wallays quickly weighed up his prospects of beating the fast-finishing Bystrom in the event of a sprint. Mindful that they still had a healthy buffer over the bunch – they led by half a minute with 3km to go – Wallays marshalled Bystrom to the front with 1500 metres remaining, and he bided his time on the Norwegian's wheel until the finish line reared into view.

"I know Bystrom, he was the strongest sprinter. It was a little uphill. I was well informed by my sport director – if I hear in the last 1.5km we had 30, 35 seconds, then I know I need to do something," Wallays said. "I stayed on the wheel because he was the strongest sprinter. I waited, I waited, I waited. I only just focused on the line, and I went with 200m to go."

How it unfolded

Few anticipated anything other than a bunch sprint on stage 18 when the Vuelta route was unveiled in January, and nothing about the opening phase of Thursday's stage suggested a deviation from that script.

Wallays, Bol and Bystrom escaped from the peloton after 3km, but their freedom came with rigorously designated limits. Sprint opportunities are few and far between at the modern Vuelta – witness the 'flat' day that finished on the climb to Caminito del Rey on stage 2 – and the fast men's teams kept a tight rein on the break's advantage throughout the afternoon.

The three leaders had 2:30 in hand after 40km, but that was as much leeway as the bunch was willing to grant them. With 80km to go, that gap had been trimmed to two minutes, and it flitted in and around the two-minute mark thereafter. A brisk tailwind only contributed to the nervousness and speed of the peloton, and there seemed but a slim prospect of the break surviving when they hit the final 20km with a lead of 1:40.

By that point, Matthias Brändle was setting the pace for Trek-Segafredo, and Quick-Step Floors, LottoNL-Jumbo and Bora-Hansgrohe would all make contributions on the rapid approach to the finish in Lleida, but despite their efforts, Wallays et al still had just shy of a minute in hand with 10km to go.

The escapees were beginning to believe more firmly in their chances, and not even the loss of Bol – distanced with a shade under 7km to go – damaged the momentum of Bystrom and Wallays, who continued to swap turns deep into the finale.

Back in the main peloton, Valverde and Yates were both tucked in right at the very front, each man mindful that there could yet be vital seconds to be won and lost on this seemingly innocuous stage.

With 2km to go, Wallays and Bystrom still had more 20 seconds in hand, but just as it seemed they would deny the sprinters, there was a sudden surge from the peloton. Sagan's mammoth effort in the finishing straight saw him move to within clutching distance of the break, but he could not quite grasp the stage victory, and the spoils fell to Wallays.

Simon Yates finished safely in the main peloton to maintain his lead over Valverde ahead of the final two mountain stages. Enric Mas (Quick-Step Floors) remains third at 1:22, with Miguel Angel Lopez (Astana) and Steven Kruijswijk (LottoNL-Jumbo) rounding out a tightly-packed top five.

A resident of Andorra, Yates is intimately familiar with the road ahead. And, having led the Giro d'Italia into the corresponding stage in May, he knows something, too, of the rarefied demands of the final days of a Grand Tour.

"It's going to be very difficult, I know that," Yates said. "I know the stages now, so maybe that helps a little bit. But it's going to be very difficult and I'll give it my best shot."

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