“Bet you never saw that one coming,” said Sam Allardyce as he swung into the press room after the match, his grin on full beam.
He was right there. When Chelsea opened the scoring here after less than five minutes, things seemed to be going precisely to expectation. This was the anticipated stroll to the title, an afternoon amble in the sunshine.
Particularly as Cesc Fabregas’s goal was the definition of simplicity, turning home Eden Hazard’s fizzing cross with practised ease. Everyone inside Stamford Bridge could predict what would come next. This was Crystal Palace they were playing after all. A landslide was the least of it.
Except the romp never arrived. Against all assumption Palace crackled on the counter. After Chelsea scored, instead of sitting back, instead of engaging in an 85-minute exercise in damage limitation, instead, in short, of playing like a Big Sam side, they piled forward with abandon and had equalised within moments. Wilfried Zaha, demonstrating with perfect timing what Gareth Southgate is missing, speared the ball beyond three leaden-footed Chelsea defenders into the corner of the net.
It was a goal whose unexpectedness provoked wild celebrations among the black-clad Palace followers. But even as the Bridge stewards were trying to put out their celebratory flares, Christian Benteke had deftly dinked home a second.
Big Sam in control, Zaha turning the home defence inside out, Andros Townsend flicking and feinting: it was as if we had been spun into an alternative universe, one seemingly constructed only after consuming a pint of chardonnay.
What made things even more confusing for the home supporters was that Chelsea were not playing badly. Every time Hazard got the ball, response seemed imminent and certain. Behind him the indomitable N’Golo Kante was parsimonious as ever in possession. His personal win percentage over the past two seasons has been an extraordinary 68.8 per cent.
But he was losing here. And as he did so, as Wayne Hennessey saved from Hazard, Nemanja Matic and Diego Costa, as Palace legs and backsides and - so it appeared on more than one occasion - hands were thrust out to block goal-bound Chelsea efforts, Antonio Conte was giving us his one-man show of pained frustration.
Even as he stamped the touchline, Palace were asking questions few have done of the league leaders this season. And most of the inquisition came from the virulently flourescent boots of Zaha. It was not that he had a lot of the ball. Unlike Kante he was not a friend to every blade of grass. For much of the time he stood in the centre circle as the action span around the Palace penalty area, apparently anchored to the turf by the expansive volume of his shorts.
It was when, finally, the ball would arrive at his feet that he demonstrated his importance. Instantly he would be away, obliging David Luiz to upend him with increasingly agricultural resolve. One sumptuous backheel to Jeffrey Schlupp took out three Chelsea players with a casual flick. And the way he outpaced Gary Cahill, drawing a desperate last-ditch yellow card of a challenge from the England man, was indicative of the danger he posed.
Every time he broke past the Chelsea line, as when Benteke neatly fed him after an hour, Stamford Bridge held its breath, watching in silence as he spun forward and shot, wheezing with relief as Thibaut Courtois deflected the ball wide with his calf. This was the player he had threatened to be as a teenager when Manchester United were persuaded to pay £10million for his potential, the player that has been largely a chimera over the intervening years.
Until Allardyce arrived at Selhurst, that is. It has proved this most unlikely alliance between inconsistent flair and unreconstructed pragmatism that has driven Palace through four successive Premier League victories, escaping the relegation maw in the process.
Under Allardyce’s tutelage, Zaha has now provided more goals and assists than Philippe Coutinho this season. He has, the manager insisted, already realised his enormous potential.
And now the pair have ended Chelsea’s twelve game victory shuffle at home. No-one, not even on April Fool’s Day, would have foreseen that.