The Motor Vehicles (Wearing of Seat Belts) Regulations 1993

2.  A certificate shall not be regarded as a medical certificate in relation to a person driving or riding in a vehicle for the purposes of these Regulations unless—

(a)it specifies its period of validity and bears the symbol shown in Part II of this Schedule; or

(b)the person is aged under 14 years and the vehicle is not a relevant vehicle.