In his first Scotland start, the Chelsea youngster was the "best player on the pitch" according to Graeme Souness, a man who knows a thing or two about being a midfielder.
His composure on the ball, range of passing and tenacity left Scotland fans applauding him off the pitch after 76 minutes.
"My God… right up there," Scotland captain Andy Robertson said when asked about Gilmour's performance. "Nothing fazes him. He can have as many caps as he wants for Scotland."
Manager Steve Clarke was also impressed, if not shocked at the Ayrshireman's talent.
"We knew before we put him in he can play, it's just getting the right moment. Tonight was his big moment and he took it and no-one was surprised by it, certainly not in our camp," he said.
Gilmour won the ball back eight times, more than any player on the pitch. It was a complete midfield performance, and one that Souness said England could have done with.
"They need a Billy Gilmour," he said on ITV. "They need a maestro. The best player on the pitch. Never gives the ball away which is fabulous for a midfielder."