In keeping with the Weightlifting competition at ExCeL, world and Olympic records were sent tumbling as Ilyin lifted superbly to repeat his success at Beijing 2008 and claim Kazakhstan's fourth lifting gold of the Games.
The 24-year-old hauled a world-beating clean and jerk of 233kg to set up a dramatic victory with 418kg.
Russia's Alexandr Ivanov, who could have really piled the pressure on Ilyin only to fail the penultimate lift of 229kg, took silver with a total of 409kg.
Bronze went to Moldova's Anatoli Ciricu after he was marginally lighter in bodyweight than Russia's Andrey Demanov following a tie on 407kg.
Ilyin insists it is a very different personal success in London compared to his gold at Beijing 2008.
'Today I feel very, very different compared to what I was four years ago in Beijing,' he said.
It's not just a gold medal for me, it's my personal triumph.Ilya Ilyin
'There I was four years younger and now I'm a different person. I've had different experiences and my personality has changed. The training was not that much different but the quality of my victory here is very, very different.
'As I said, I've changed, and I think last year in Paris (at the World Championships) I was already different but here, at the age of 24, I gave everything for this triumph. It's not just a gold medal for me, it's my personal triumph.'