What butterfly will this turn into?

What butterfly will this turn into?

Observation - What butterfly will this turn into? - UK and Ireland. Description: Saw this in a wet grassland, do you know what it could turn into? On the same day I saw a red admiral and a small copper could it be the caterpillar of any of these?

Saw this in a wet grassland, do you know what it could turn into? On the same day I saw a red admiral and a small copper could it be the caterpillar of any of these?