Sch 1 para 4
(1) A person charged under section 143 of the Road Traffic Act 1988 with the offence of using, or causing or permitting the use, of a motor vehicle so as to contravene that section (driving uninsured) may prove as a defence that the vehicle was being used by authority of the Secretary of State under section 4(2) of this Act and that— (a) it was at the material time the subject of insurance or security complying with Part VI of the 1988 Act ; and (b) pursuant to arrangements made by or with the Secretary of State for the purposes of section 4(2), the insurance or security is treated as extending to its use on that occasion. (2) A person charged under section 165 or 170 of the Road Traffic Act 1988 with an offence of failing to produce the relevant certificate of insurance or certificate of security within the meaning of Part VI of that Act may prove as a defence that the vehicle was being used by authority of the Secretary of State under section 4(2) of this Act and that— (a) he produced a certificate of insurance or certificate of security complying with Part VI of that Act; and (b) pursuant to arrangements made by or with the Secretary of State for the purposes of section 4(2), the insurance or security to which the certificate relates is treated as extending to the use in question.