Wiring for towing 2005 Ford Ka behind motorhome

Can someone please assist me?

I need to know which Ka loom cable to splice into with the 7 core cable that comes from the motirhome?

(I already have a diagram showing me which motorhome wire matches which Ka wire)

I am hoping someone may have done this and would be able to explain or show with photo the location under Ka bonnet of the loom cable to use for making this connection?

Any guidance would be much appreciated.