reg 9 Period of validity of medical fitness certificate
A medical fitness certificate is valid only from the date of the medical examination or the date of consideration by a medical referee, as appropriate, and for the following maximum periods— (a) in respect of a person under 18 years of age, one year, (b) in respect of a person of 18 years of age or over, two years, or, in either case, such shorter period as is specified on the certificate.