WARNING: This page is about a different car, the 2010 MINI Cooper, 2009 MINI Cooper, and 2008 MINI Cooper. However, it is still accessible from the selected car via links, so may be relevant.
Unlock hook (1) with special tool 61 1 360 and slide plug housing downwards out of base.
Fig 1: Unlocking Hook With Special Tool (61 1 360)