A category K driving licence is required to drive a mowing machine or vehicle, which is controlled by a pedestrian. A person must be at least 16 years old before they can hold a category K driving licence. You will inevitably have this as well as a Cat F Tractor licence.

This is from: www.gov.uk/guidance/agricultural-vehicle-licences-...l

Tractors
A tractor qualifies as an excepted vehicle if it is designed and constructed primarily for off-road use. *** An excepted tractor can be used on a public road solely for:

agriculture, horticulture or forestry work ***
cutting verges bordering public roads
cutting hedges or trees bordering public roads or bordering verges which border public roads

Light agricultural vehicles
For a vehicle to qualify as a light agricultural vehicle, it must:

have a revenue weight not exceeding 1,000 kilograms
be designed and constructed so as to seat only the driver
be designed and constructed primarily for use otherwise than on roads ***
be used solely for purposes relating to agriculture, horticulture or forestry
The revenue weight of a vehicle is either the maximum weight of the vehicle or the design weight as defined in section 60A of the Vehicle Excise and Registration Act.

Quad bikes and similar single-seater machines used for agricultural, horticultural or forestry work are classed as light agricultural vehicles.

Agricultural material handlers
For a vehicle to qualify as an agricultural material handler, it must be designed to lift goods or burden. It must also be designed and constructed primarily for off-road use. ***

This category is restricted to material handlers used on public roads solely for:

agricultural, horticultural or forestry work
cutting verges bordering public roads
cutting hedges or trees bordering public roads or bordering verges which border public roads