Blues manager Emma Hayes – pictured lapping up the fans’ adulation after defeating the Gunners – is keeping her tactical secrets to herself, rather than telegraphing them to other coaches.

She refused to reveal the precise instructions she gave her team at half-time in the London derby against Arsenal, who bounced back from their weekend defeat by beating Slavia Prague 5-2 away in the Champions League, preferring instead to let the journalists assembled at Kingsmeadow after the weekend’s victory draw their own conclusions.

“I did something… but this is a really tricky one. Because I don’t want to tell you how I did it – their manager is then going to read those comments and make sure he doesn’t do it again!”

Hayes grinned, surveyed the rows of sports hacks in front of her, and added: “That’s for you to analyse; that’s your job.”

So what did change in the second half to achieve the extra oomph that paved the way for a famous turnaround, silence the usually strident Gooner fans and send the Blues supporters home with a real spring in their step?

It was partly a better, more urgent use of wing-backs in Maren Mjelde on the right and Jonna Andersson on the left (though Andersson’s positioning still left room for improvement as she could have made fuller use of the Kingsmeadow pitch width).

But it was also a general ratcheting up of aggression and pressing, typified by Erin Cuthbert’s wholehearted challenge in midfield which freed up Fran Kirby to race forward and square for Beth England’s leveller just before an hour had passed.

In addition, woman-of-the-match Ji So Yun moved into a more forward position after a reshuffle involving the 75th-minute withdrawal of Guro Reiten and Kirby.

During the four minutes that followed the substitutions, Ji twice went closer, with a header and a firm shot that just went wide.

“Ji So Yun is unbelievable… literally,” said Hayes afterwards, quoting from the Blues fans’ terrace chant for the influential Korean.

After Ji went off with cramp (she’d just returned from the States, where she was on international duty) to be replaced by Drew Spence, the relentless pressure continued, eventually leading to the winner by sub Maria Thorisdottir, fed by fellow sub Ramona Bachmann.

The Gunners turned the screw late on, as Chelsea clung on, and Beth Mead could easily have equalised in the dying moments after nutmegging a defender. But Berger in the Chelsea goal was ready, dived to her right and got a hand to the shot.

Mercifully for Chelsea, the packed defence was able to hoof the loose ball clear before an Arsenal player could fire in a follow-up shot.

“We did something,” admitted Hayes, when pushed to reveal more about her half-time alterations. “We said we’re either all going to do it together, or not at all, and that’s what I felt happened. It’s not that difficult! Football is not that complicated.

“I said to them I hate platitudes like ‘You’ve got to want it more than them’, but I felt today that that rung true more than not. I thought that belief grew in the second half, and Arsenal tired. I think they ran out of ideas, but that – in part – is due to how [our] team set up and organised.”

The Gunners may have run out of ideas at Kingsmeadow, but three days later in a memorable evening in the Czech Republic, Joe Montemurro’s women turned the pain of defeat into the motivation for a hefty away victory against Slavia Prague, with Vivianne Miedema (a subdued presence against Chelsea) scoring four. “It’s always good when you can instantly go again after losing a game,” said Miedema after the Prague match.