All prosecutions for the public interest before the High Court or before the sheriff sitting with a jury shall proceed on indictment in name of Her Majesty’s Advocate, and such indictment may be in the forms set out in Schedule A to the M1Criminal Procedure (Scotland) Act 1887 or in an Act of Adjournal under this Act or as nearly as may be in such form and shall be signed by the Lord Advocate or one of his deputes, or by a procurator fiscal, and the words “By Authority of Her Majesty’s Advocate” shall be prefixed to the signature of such procurator fiscal.