Section 429 of the Companies Act 1948 (which prohibits the formation of a company, association or partnership consisting of more than ten persons for the purpose of carrying on the business of banking unless it is registered as a company under the Companies Act 1948, or is formed in pursuance of some other Act, or of letters patent) shall not prohibit the formation of a partnership consisting of not more than twenty persons each of whom is for the time being authorised by the Board of Trade to be a member of a partnership formed for that purpose and consisting of not more than twenty persons.