Thanks for all the water in boot posts which helped me find the problem.
This grommet isn't in the hole, I have tried to get it back in but the pipe is under too much tensions against the black plastic side panel, so I am concerned it will just work loose again.
I would like to know what the pipe through the grommet is as it looks like it's chaffing?
And should I try to get grommet back in and smother the hole in roofing mastic, or leave as is and smother in mastic?
Thanks.

Bockhamptoner said:

I would like to know what the pipe through the grommet is as it looks like it's chaffing

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It's probably the wiring harness for the tow bar electrics, not a pipe.

Thank you that makes sense and why it doesn't fit behind the panel and has pushed the grommet out.

Bockhamptoner said:

Thank you that makes sense and why it doesn't fit behind the panel and has pushed the grommet out.

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Maybe the wiring to the tow bar is too short. It's supposed to enter the vehicle behind the panel, through another hole. This is then hidden from view, and right by the plug in connection to the vehicles wiring harness.