The Jaguars went 10-0 in front then looked to have sealed victory with just under four minutes left when Travis Etienne scored with just under four minutes on the clock.
But KJ Hamler collected a 47-yard pass to set up Murray for the crucial score to seal a thrilling win and improve the Broncos’ record this season to 3-5.
The Jaguars, playing in London for the ninth successive year, arrived on the back of four straight losses but confident of victory against a side failing to live up to pre-season expectations.
Broncos quarterback Russell Wilson returned to the team after missing last weekend’s defeat to the New York Jets through injury but endured a rough start, throwing an interception on Denver’s second possession.
And the turnover proved costly as Jaguars quarterback Trevor Lawrence quickly connected with tight end Evan Engram for a 22-yard touchdown midway through the first quarter.
Denver’s defence gave their side a boost when Lawrence was brilliantly intercepted by Justin Simmons in the end zone as it looked like Jacksonville were going to add a second touchdown.
But the Broncos offence failed again and Jacksonville’s next possession ended in a Ryan Patterson field goal to make it 10-0.
As the game approached half-time, Denver finally sprung to life. Wilson led a 75-yard drive down the field and wide receiver Jerry Jeudy rushed in from six yards to get the Broncos within three points at half-time.
Denver clawed their way back early in the second when Wilson booted them upfield, including a 38-yard pass to Greg Dulcich that saw Melvin Gordon go over from close range.
Etienne looked to have salvaged success for Jacksonville before Murray snatched a dramatic late victory for the improving Broncos.