Closure apparatus and method of closing an opening

A method of closing an opening formed in a collar, comprising:

• moving a closure from an open position to a closed position, said closure closing said opening in said closed position, and said closure comprising:
• a collar having a collar periphery and having a collar inner surface defining an opening,
• a closure periphery, said closure being for closing said opening,
• a bearing structure being located around said collar periphery or said closure periphery, a locking ring being mounted for rotation with respect to said closure and said opening on said bearing structure, so that said locking ring is rotatable between a locking position for locking said closure to said opening and an unlocked position for permitting said closure to be moved away from said opening;
• and
• rotating the locking ring from an unlocked position to a locked position, wherein said collar has a collar outer surface and at least one engagement formation formed on said collar outer surface, said closure having a closure outer surface with at least one second engagement formation formed on said closure outer surface, said locking ring having a locking ring inner surface and at least one third engagement formation and at least one fourth engagement formation formed on said locking ring inner surface, said locking ring being configured so that said third engagement formation engages one of said first and second engagement formations in said locked position to hold said closure in said closed position and so that in said unlocked position, said fourth engagement formation is spaced apart from said other of said first and second engagement portions, to permit said closure to be moved into said open position,
• wherein said closure is mounted on a closure carriage, said closure carriage comprising a closure grip for releasably engaging said closure, and
• wherein said closure grip comprises at least two closure grip parts and said closure comprises at least one closure grip mount, a closure grip part drive being provided for driving the first and second closure grip parts to engage said closure grip mount.