What are 'spring assisters'?

[the fury]

There's a classic 900 turbo I have my eye on to buy, but it has a towbar fitted. Previous owner said it was used to tow a caravan and it is fitted with spring assisters - what are these exactly and will they affect the handling? If so, are they easy to take off (along with the towbar itself?) Would towing a caravan do any damage to the car you reckon?

[Prof Beard]

I was going to reply to this but noticed an excellent reply to your question in "General Gassing" - what they said!