LONDON – Down 4-0 after just 36 minutes, Julen Lopetegui was in danger of being the only West Ham-linked man left in the stands.

The Hammers boss, who served a one-match ban on the sidelines after picking up three yellow cards this season, watched from a high vantage point as fans poured out of the London Stadium around him before half-time, shaking their heads in disbelief at the devastation . Arsenal surprised. And yet, four minutes later, out of nowhere, West Ham had scored two goals. Hope was brought to life.

Just as the Hammers were getting into a position to mount a second-half comeback, keeper Lukasz Fabianski punched Gabriel Magalhães to concede a penalty which Bukayo Saka converted to send it 5-2 to the Gunners at the break.

It was, quite simply, absolute madness — a brilliant advertisement for the brilliantly chaotic, improbably unpredictable product of the Premier League, which ranks as one of Britain’s most successful global exports in any field. In the end, the seven first-half goals tied a league record with three other matches, the last of which came between Reading and Manchester United in December 2012.

Judging by the relative lack of empty seats – most of the beleaguered West Ham fans returned anyway – it was amusing that just when it looked like more of the same would follow after the break, the other side was goalless and uncompetitive . It felt like the proverbial early night in bed after happy-hour hedonism. So with about 15 minutes to go they started walking again. It is, as always, the hope that kills you as a sports fan and West Ham’s had long been extinguished.

Meaningful conclusions from matches like this are inappropriate, but it should still be noted that after Arsenal needed a set-piece to break the deadlock, some of their football was a combination of divine and deadly.

Gabriel Magalhães’ 10th-minute header was the final act in a set routine that will bring Arsenal fresh credit even given their well-documented strength in these situations. Gunners ran from far to close, was a blur of movement, where perhaps the most cunning action was Jurriën Timbers gentle push on Lucas Paquetá to ensure that Saka’s delivery found Gabriel unmarked.

If the dark arts helped break the deadlock, Arsenal well and truly stepped into the light.

Chrysencio Summerville had a 17th-minute effort correctly ruled out for offside but West Ham were then overrun, Martin Ødegaard and Saka combining superbly to put in a simple finish for Leandro Trossard. Saka then moved into the box and Paqueta could do nothing but bring him down. Ødegaard converted. Trossard then released Kai Havertz who finished low past Fabianski to show the first mini-exodus.

West Ham were the heavyweights, knowing they were losing on points and so were reduced to hopeful haymakers; inexplicably they began to land. Carlos Soler was given too much space in Arsenal’s defensive third, although his pass was excellently carried through for Aaron Wan-Bissaka to castle home. Wan-Bissaka had scored two goals in 182 Premier League appearances, but now has two in six days. Because why not?

Perhaps even more unlikely, Declan Rice conceded a dubious free-kick awarded for a challenge on Paqueta, and Emerson Palmieri curled a superb 25-yard free-kick off the bar. It was the left-back’s second goal in 20 months.

Just as the visitors’ sudden loss of composure brought back memories of Arsenal’s 4-4 draw with Newcastle in February 2011 – the only time a Premier League side has failed to win a game in which they led by four goals in the first half – Fabianski accidentally floored Gabriel when he tried to meet a corner and Saka slotted in the penalty to end the scoring. Thankfully for them, the three-goal cushion proved sufficient.

Arteta enjoyed the restoration of flow to Arsenal’s play, sparked most significantly by Ødegaard’s return to the starting line-up; It is no coincidence that the Norwegian’s reintegration came in a week when the Gunners scored 13 goals, including five in the Champions League, for the first time since 2008.

There was a warning after that match, which here too proved to be prophetic. “Before and after half-time you have to get through those 10-15 minutes in a different way,” Arteta said after Tuesday’s 5-1 win in Lisbon. “We gave away so many balls, and that doesn’t allow you to get results.”

There was a similar sloppy spell here and there may come a time when it becomes the topic of discussion. But not today, not after a 45-minute period that ranks among the most tumultuous in recent memory.