New towing rules

I've just come across the new licensing rules and am interested in the trailer towing rules from 19 January 2013 http://www.direct.gov.uk/en/Motoring/DriverLicensing/DG_201202 )

It says, "If you already have a licence to drive cars or small vehicles (category B and BE), you'll keep your entitlement to tow trailers. Your entitlement to tow trailers will stay as it was when you passed your driving test. ... To tow heavier trailers after 19 January 2013, you'll need to follow the rules for new drivers..." The rules for new drivers, of course, say that they must take a BE test to tow "heavier trailers."

I have "grandfather rights" and am therefore currently able to tow my large caravan with my large 4x4, without having taken a test. The question is, what does "heavier trailers" actually mean? Does it mean trailers heavier than 750kg, or trailers heavier than 3,500kg? Are we all going to have to take BE driving tests?!

Iis there someone on the forum who is in the know about these new rules? It's possible that this alteration to the rules is simply in relation to trailers heavier than 3,500kg, but the wording is unclear. Direct.gov can be a difficult web site to understand.

Many thanks