In general, the minimum ages for driving on British roads is 16 years for invalid carriages and mopeds, 17 years for agricultural or forestry tractors, small vehicles and motorcycles, and 21 years for medium/large sized vehicles, minibuses and buses.
At 16 years old a person can drive a 3-wheeler that is powered by an engine no greater than 50cc. You have to be 17 or over to drive a larger 3-wheeler like the Reliant Robin. (750cc - 850cc). However; A 16 year old enititled to Disability Living Allowance at the higher rate (Mobility Allowance) may drive a Microcar
FAQ by 16 year olds: