The army rolled into Las Rozas at 0945 hours on Friday. A dozen personnel, including a colonel, a captain, a lieutenant, two sergeant majors and three corporals, arrived at Spain HQ early on a mission to vaccinate the national team against Covid-19, three days before their opening game at Euro 2020. In total, 43 injections were administered by staff from the Gómez Ulla military hospital, the few who already had the first Pfizer jab getting their second, while the rest got the single-dose Janssen. And then the players went back to their rooms, alone.

Spain’s manager, Luis Enrique, insisted that the federation had asked more than a month ago for their players to be vaccinated, a formal written request landing at the ministry of health last week. “I would have liked it to have been done when it should have been done, after naming the squad,” he added. Now it had actually happened, the government calling the army in – because, in Jordi Alba’s words, they had “seen the wolf’s ears”, the danger right before them.

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It was their 12th day at Las Rozas, 25km north-west of Madrid, difficult days. “Not pleasant,” Luis Enrique admitted. Not ideal preparation for the Euros, either.

There had been noise from the start, more than there needed to be. Sergio Ramos, the captain, had been left out of the squad after barely playing in 2021 and not a single Real Madrid player was called up. In their first warm-up game against Portugal, some supporters had whistled Luis Enrique and at full time chanted: “How bad you are!” at striker Álvaro Morata. But that was nothing compared with what was coming and by the time their second-warm up game arrived, they couldn’t even play it.

Sergio Busquets had tested positive for Covid-19 after the Portugal game. “Everything falls down and you start to doubt,” Luis Enrique admitted. Spain activated the protocols. Taken home in an ambulance, Busquets went into quarantine for 10 days and Las Rozas was locked down, players isolated in their rooms, while the under-21s were called up to fulfil the fixture with Lithuania.

That was easier said than done; most were on holiday. Like a Sunday league team, the federation began frantically ringing round, players hurriedly packing bags. They gathered together a team in “record time,” said Luis de la Fuente, the under-21s coach who had been called back from his home town of Haro. The squad was officially announced at 1.30am. Having travelled to Madrid and waited for PCR results, their first training session did not even start until 10.30pm the next day.

On Tuesday evening, Spain’s European Championship squad sat and watched Spain play on television. The game, officially a senior international, will make a great pub quiz question one day: 16 players and the manager made full debuts, four debutants scored and two debutant keepers kept a clean sheet in an impressive 4-0 win. After the game, though, more bad news arrived: Leeds United defender Diego Llorente was confirmed as the second senior player to test positive for Covid-19. “Devastating,” he called it.

The possibility of an outbreak was real, even the risk of Spain not making it to their first match against Sweden at La Cartuja in Seville. Busquets had been inside Spain’s bubble for six days, after all. The federation had already set in motion their contingency plan. On Monday, Celta Vigo’s Brais Méndez was called up, leaving his holiday in Mykonos to head to Madrid.

Brais was not Busquets’ replacement, as initially assumed; instead, he turned out to be one of four players called up, alongside Pablo Fornals, Rodrigo, and Carlos Soler. Raúl Albiol was subsequently added to that group, and then so was Kepa Arizabalaga.

After the Lithuania match, 11 players from the under‑21s joined them in a parallel squad, an entire national team working in a separate bubble and held in reserve in case needed. They had answered the call “in three minutes having been promised nothing”, Luis Enrique noted.

The reserves trained at Las Rozas, but stayed in a hotel near Plaza de España. The original squad remained isolated and continued working, but not the way they had wanted it. Communal areas were removed, players ate in shifts and socially distanced. There were no video sessions: the last thing you could do was gather them together indoors, Luis Enrique said. Training was individual, focused on fitness.

On Wednesday, group work was resumed but not in the normal way. The squad was split into two groups of 10 by position: in effect two teams in two bubbles, on the pitch and off it. If one fell, the idea ran, the other hopefully would not. As Luis Enrique explained: “[Left-backs] Jordi Alba and Gayá can’t come within 10 metres of each other. The right-back can’t mix with the right-back, the centre forwards, the goalkeepers. It’s two different XIs, a right-winger in each, a striker …”

Three sessions ran daily, usually at 5.45pm, 6.45pm and 7.45pm, the hottest hours chosen to emulate likely conditions in Seville. Even within those groups, training remained incomplete with most of the work remaining individual, although some minor tactical preparation was done – throw-ins, restarts. In the open air, with all the gym equipment arranged under mini marquees, at least the coach could speak to players. “They’re not ideal conditions,” Luis Enrique said, “but there’s no excuse. We’re among the six or seven favourites for sure.”

The restrictions remained. “We’re in that tunnel where we do what they tell us; we’ll do everything they say to make it to that first game,” Thiago Alcântara said. “We’re anxious to be a group again, in the literal sense.”

Every day there were PCRs, the players woken early and tested at 8am to give the lab time to return results as soon as possible. Each test brought tension: “What if …?” Luis Enrique insisted: “There is that uncertainty and that affects you whether you like it or not. It creates unease. But that’s why we have Joaquín [Valdés, the psychologist] here and what we have seen in training is spectacular.”

Related: Álvaro Morata and Spain booed by home crowd after friendly draw with Portugal

Good news followed: a full day of negative test results, then another, then another. The government agreed to administer the Pfizer vaccine but there were concerns about side-effects having left it so late and negotiations continued: eventually, it was agreed that the players would get a single-dose vaccine. Diego Llorente too tested negative, that initial result revealed as a false positive. There was relief, cautious optimism returning. Spain were at last getting there. They could start again, even if still without their captain Busquets. They would wait for him, Luis Enrique said.

On Friday, after four negatives, Llorente returned to Las Rozas, handed a standing ovation as he walked back in. “I needed that,” he said. “We’re seeing the light at the end of the tunnel a bit, and this will make us stronger.”

On Saturday morning, the parallel squad were given a guard of honour, honourably discharged, their work here done no longer needed. And then, that afternoon the Spanish national team finally trained together – two days before their opening game. A small step that was a major triumph. Asked about their hopes of making it to the final at Wembley, Thiago had summed it up: “What we want now is to get to La Cartuja,” he said.