Note! you cannot tow a trailer that is 3,500kgs gross even empty - legally.
Yes you can!
From IFor Williams ( who know a lot about trailers) FAQ
My vehicle has a maximum towing weight of 1500kg and my trailer has a maximum gross weight of 2000kg. Can I still tow this trailer?
Yes, as long as the unladen weight of the trailer you are towing combined with the trailer load does not exceed 1500kg, then you can tow this trailer with your vehicle.
There is no legal requirement to downrate the plate on your trailer.
Extract from the NTA website says the same thing worded slightly differently.
Working out what your car can tow can be very confusing. There is so much information on the web – much of which is conflicting.
The total weight of your trailer must not weigh more than the car’s maximum towing capacity (MTC).
Contrary to popular belief, you do not need to take the trailer’s maximum authorised mass (MAM) into consideration – unless you passed your test after 1 January 1997 (more on this later). It is the actual weight of your trailer that needs to be taken into account.
So, if your trailer weighs 700kg and your contents weigh 500kg, the actual weight is 1200kg. This is the weight your car needs to be capable of towing. Even if your trailer’s MAM is 2000kg, it is irrelevant, unless you plan on towing that weight.
“You can’t be penalised for towing something that could potentially go over your car’s maximum towing weight,” said a DVLA spokesperson. “It would be like fining someone for doing 30mph in a 50mph zone – because they could potentially go over the speed limit. If you are within the limits you are legal.”