7. A medical fitness certificate is valid from the date of the medical examination or date of consideration by a medical referee appointed under regulation 11(1), as appropriate, and for the following periods—
(a)in respect of a person under the age of 18 years of age, one year;
(b)in respect of a person over 18 years of age, two years; or
(c)in either case, such shorter period as is specified on the certificate.