6Where a person has committed an offence under section 23 of the Solicitors Act 1974 before the commencement of section 7 of this Act, he shall not be liable after that commencement to be proceeded against in respect of that offence unless the act constituting that offence would have constituted an offence under section 23, as substituted by section 7 of this Act, if it had been in force at the time when the act was done.