Palmer, who was introduced as a second-half substitute, was lively on the right flank and curled a stunning strike into the top corner with just under 15 minutes remaining.
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Leandro Trossard equalised with a deflected effort deep into stoppage time, before the Gunners emerged victorious on spot-kicks.
The 21-year-old was disappointed to lose, but proud after his special moment at Wembley.
“Obviously disappointed to concede in the last minute and then penalties. But that’s football,” he said. “We dug in deep. It is what it is.
“We played well. It’s the first official game of the season, so it’s about momentum building and stuff.
Of course, scoring at Wembley for the club you’ve been at since the age of seven, is a proud moment.
“But it doesn’t count for much at the end of the day, but obviously it’s a nice feeling.”
The Academy graduate also spoke about the length of stoppage time added on by the referee, his personal fitness and the upcoming 2023/24 Premier League opener against Burnley at Turf Moor.
Hear all his thoughts by clicking the video at the top of the page.
