I have been dealing with a number of such hearings recently; whether for permission to make an application under s8 of the Children Act 1989 or for permission to apply to discharge a Special Guardianship order.
Applications to discharge a Special Guardianship Order are governed by s14(D) of the Children Act 1989. S14D(3) identifies the people who require the leave of the Court before making the application and s14D(5) stipulates that the Court may not grant leave [to any applicant other than the child] unless it is satisfied that there has been a significant change in circumstances since the making of the special guardianship order.
When dealing with these applications practitioners might find it helpful to point the Court to the Court of Appeal authority of Re M (Special Guardianship Order: leave to apply to discharge)  EWCA Civ 442
I have found it useful to refer the Court to the following paragraphs in particular:
To sum up, when a court is considering an application for leave to apply to discharge a special guardianship order, it must first consider whether the applicant has shown, by means of credible evidence, that there has been a significant change of circumstances since the order was made. If there has not been, the application will fail. If there has, the court will decide whether leave should be granted, based on a realistic evaluation of the applicant’s prospects of success in the context of the effect on the child’s welfare of the application being heard or not heard. The prospects of success must be real. The child’s welfare is an important factor but it is not the paramount consideration. The degree of any change in circumstances is likely to be intertwined with the prospects of success, and the greater the prospects of success, the more likely it is that leave will be granted. The provisions of s. 10 (9) of the 1989 Act are not applicable to an application under s. 14D (5).
2. paragraph 28 which gives assistance in relation to the word “significant”
I therefore conclude that the requirement under s. 14D (5) for a change in circumstances to be significant means what it says and, to this extent only, I would not follow the provisional reasoning in Re G. If more is needed, ‘significant’ in the context of the s. 31 threshold condition means ‘considerable, noteworthy or important’, according to the dictionary definition cited in the Guidance when the 1989 Act first came into force (The Children Act 1989: Guidance and Regulations (Volume 1, Court Orders) (HMSO 1991)), as approved by Baroness Hale in Re B (Care Proceedings: Appeal)  UKSC 33;  2 FLR 1075 at . As Ms Cabeza says, it does not mean trivial or unimportant, and neither does it mean exceptional, immense, or insurmountable.
3. paragraph 29 which addresses the second stage of the test
Turning to the second stage, what has to be shown in a case under s. 24 (3) is broadly “a real prospect” of success: see Warwickshire (1) at . In my view, the same approach should be taken in a case under s. 14D (5). Likewise, echoing relevant elements of the guidance given in the adoption context in Re B-S (Adoption: Application of s. 47(5))  EWCA Civ 1146;  1 FLR 1035 at , the degree of any change in circumstances is likely to be intertwined with the prospects of success, and the greater the prospects of success, the more cogent the welfare arguments must be if leave is to be refused.
4. and paragraph 46 in which the Court is warned against applying the incorrect test
At the second stage, the Judge appears to have taken the approach that if there was any risk that proceedings might undermine the stability of C’s placement, the application for permission should be dismissed. This was not the right test. There was no real assessment of the prospect of success. A range of facts were assumed against the mother, while the grandparents’ narrative was taken at face value. The statement that there would be care proceedings or placement in foster care was unsound. There is no consideration of the possible advantages of proceedings for C. Any court applying the correct test would conclude that the mother’s case had solidity and should be investigated.
As confirmed in this authority the test under s10(9) Children Act 1989 is not applicable in proceedings concerning the discharge of a Special Guardianship Order.
s10(9) Children Act 1989
You may well have to consider this section in addition to s14(D) as many parents seeking to discharge a Special Guardianship Order may also wish to secure a Child Arrangement Order either (i) to protect or increase their contact regime over the period of the proceedings or any assessments (ii) to ensure that they have a certain frequency of contact in the future if their application to discharge the Special Guardianship Order is not successful or (iii) to formalise the position of the child living with them in the event that an Order discharging the SGO is made.
The test under S10(9):
Where the person applying for leave to make an application for a section 8 order is not the child concerned, the court shall, in deciding whether or not to grant leave, have particular regard to –
Do remember that whilst a parent whose child is subject of a Special Guardianship Order to the child’s grandparents would not require permission to make an application for a s8 “spend time with” order; permission is required (by s10(7A) & s10(7B) in circumstances where that parent seeks a “lives with” order.
This may result in the Court needing to deal with two applications for permission governed by different tests.