My 2015/65 SEL Exec has a detachable swan neck Westfalia tow hitch. How do I determine if my car has trailer assist?

I don't think trailer assist was available then.

Not too sure it's available now either but hopefully someone can say.

 

My MY 2018 L&K with a factory tow bar certainly hasn't got it.

Do you get the secondary +1 indicator flashing when trailer is connected. If you take a bulb out of the trailer the dash should tell you it’s the trailer and exactly which bulb is out. Can’t remember which module it’s in, but depending on who fitted the towbar, the trailer adaption should be selected as well. It alters esp correction to allow for the trailer when it’s hooked up to the electrics.