Size of E-socket needed to for Anti-Roll Bar?

Hi everyone, I have a Laguna MK2 Sport Tourer 2003 and need to replace the rear subframe bushes. I have the bushes and the tool but have noticed that the anti-roll bar appears to be attached with a bolt through the bush. Does anyone know what size e-socket is needed to remove the long bolt? I have a 16mm e-socket but it is larger than that.