‘The Lionheart’, from Meopham, won all four rounds of the Matchr00m-promoted bout, which was televised live on Sky Sports.
“It was an amazing atmosphere,” said Syrett, who had never fought at the London 2012 Olympic venue.
“When I turned up and saw the arena I was excited, I just wanted to enjoy the moment.”
His opponent, an 18-year-old from Bulgaria, had come in to replace Serge Ambomo at late notice.
“It was my best performance to date,” Syrett told the Times. “He’d never been stopped.
“I only found out I was fighting him a couple of days before. The other opponent was only 5ft 3in, which is unusual for a middleweight, and I hadn’t found anyone that small to spar with.
“But this guy was the same size as me and I was used to sparring with people of my height.
“I won every round, but I got a bit carried away early on,” he admitted. “The occasion got to me a bit and I wanted to take him out.
“I got too close and should have picked my shots. When I relaxed, I got into the fight more.”
Syrett will take time off with his fiancée Lily Fleet-Newman before moving up to six rounds for the first time in his next bout, against an undisclosed opponent at York Hall on June 8.
“I’m moving up to six rounds next, which suits me better, to be honest,” he said.
“I’ve been training 10 rounds to get my sparring partner ready for a Southern Area title fight so I’m used to it – and I’m certainly fit enough.”