Ianto hadn't meant to press the button it just happened. When Jack told him not to press the tiny button on Jack's wrist strap he promised he wouldn't, He didn't know why Jack had taken it off anyway he never took it off. Ianto had sat there with it as Jack left the room he was fine about it but there was something nagging inside him telling him to press it like a younger version of himself telling him to press the button.
It didn't stop either, he put it to one side as he started to make coffee to try to distract himself but he kept looking over at it just lying there with its many buttons and that one button in particular that was calling out to him.
Finally the overwhelming urge was to much for him and he grabbed the strap and pressed the button.
