Must have Category B licence, aged appropriate to the weight of the dumper, check it is insured for such use, seat belt must be work (must be worn anyway). Dumpers are classed as exempt goods vehicle.

Red diesel?

I believe you cannot use red diesel on the road except for short journeys. Though I don't know what the limit would be.

8.15 Works trucks
To qualify as a works truck the vehicle must be a goods vehicle designed for use in private premises. It must only be used on public roads:

(a) for carrying goods between private premises and a vehicle on a road within one kilometre of those premises,

(b) in passing from one part of private premises to another,

(c) in passing between private premises and other private premises in a case where the premises are within one kilometre of each other, or

(d) in connection with road works at the site of the works or within one kilometre of the site of the works.

In the context of this category a goods vehicle is a vehicle constructed or adapted for use and used for the conveyance of goods or burden of any description (whether in the course of trade or not).

Typical works trucks include fork lift trucks, ‘shunt’ vehicles designed to haul articulated trailers and their goods around sites and special vehicles which lift and move freight containers around sites. Typically, the vehicle will have a maximum speed well below road traffic speeds of 30 mph+ and will lack many of the features, such as braking and lighting systems, required under the Road Traffic Act 1988.

http://customs.hmrc.gov....MCE_CL_000164#P181_16924

Or land rovers, and other diesel cars they own ;-)