Any agreement or consent which is required by this Act to be given to the making of an order or application for an order ... may be given in writing, and, if the document signifying the agreement or consent is witnessed in accordance with Family Procedure Rules, it shall be admissible in evidence without further proof of the signature of the person by whom it was executed.
A document signifying such agreement or consent which purports to be witnessed in accordance with Family Procedure Rulesshall be presumed to be so witnessed, and to have been executed and witnessed on the date and at the place specified in the document, unless the contrary is proved.