Within the overall framework defined by the structures and authorities as set out in Article 21, the functions described in Article 28 may be grouped and assigned to specific bodies within or outside the operating structures initially designated. This grouping and assignation shall respect the appropriate segregation of duties imposed by Regulation (EC, Euratom) No 1605/2002 and ensure that the final responsibility for the functions described in the said Article shall remain with the operating structure initially designated. Such a restructuring shall be formalised in written agreements and shall be subject to accreditation by the national authorising officer and the conferral of management by the Commission.