According to the info I have ...
http://homepage.ntlworld.com/andrew.reynolds983/Manuals/Omega2002Manual.pdfpage 224
The kerb weight of a 3.0 MV6 is not listed .. so using the figures for a standard 3.2 elite ... and the figures of my VIN plate - which are .. spookily .. the same ..
Gross vehicle weight : 2200 kgs
Gross train weight : 4075
this gives a maximum "tow" weight of 4075-2200 = 1875
The subject car is a 2.5 TD -gross weight not listed but using the 2.6 as a comparison .. 2180 (ish)
so without the trailer already some 300 kgs over the top ..... now add a large and heavy twin axle trailer.....
Remember ... Police don't care about ACTUAL weights .. they always go by PLATED weights, VOSA might do actuals, polce won't IME ..