From "EastEnders: Episode dated 3 February 2005"
[a naive Lucy has recounted a story about her dad, Ian, and Jane. She has noticed uncharacteristic behaviour such as her dad plays music in his bedroom nowadays
You do know they'll doing it, don't you?
What you think they... you know... gone all the way?
It sounds to me like they've gone all the way, turned round and come back again!