Agricultural tractors are vehicles designed exclusively or primarily for agricultural purposes whether or not permitted for use on UK roads opened to public traffic.
Examples include combine harvesters and high speed tractors.
Here are two examples to help you identify the details requested by NOVA.
Make: John Deere
Series (model): SR
Version (derivative): 5090M
Brake Horse Power (BHP): 90
Make: Massey Ferguson
Series (model): MF8600
Version (derivative): 8650
Brake Horse Power (BHP): 240
All of the information referred to above should be available on the vehicle purchase invoice and in the vehicle manual.