Shock Links

Hi all-I am new to all this. 

However I've been looking at the internet and noticed several threads that say a leaf sprung vehicle requires a shock link fitted between the tow bar and the ball. I have just purchased a van with an AL.CO chassis and tow hitch. (Bailey Unicorn Valencia) I have an L200 long wheel base and when I picked the caravan up  none of the after sales persons or the fitter who changed the tow ball said anything. Can someone put me out of my missery and give me e definitive answer.

I am not inexperienced when it comes to towing as I have a Class 1LGV license and towed all sorts of trailers but I have seen so much conflicing information I just cannot make up my mind.

Thanks.