I always use the sensible rule ....;
If it looks sensible the chance of being stopped reduces.....as I have a 'few' grey hairs and a Hyundai I've never been stopped ....I have towed 'normal' sized things ( not huge triple axle boat trailers or great big yachts)
When I had a 1.1 escort aged 17 I used to tow all sorts (just) and was stopped a few times...
Luke being a 'youth'
driving a Saxo
towing a quick fancy looking boat
= pulled over ....
The fact of where he lives and they maybe have one copper to cover eveything may be his saving grace.
Just the way I see it .....