You now need form AB/CB/FL/RET/APP/2015(Revised).
That's the application form to seek an AB/CB/FL/RET/SUBMISSION which, in turn, is the form you require to seek retrospective flouncing permission.
The form should be read in conjunction with the appropriate notes (AB/CB/FL/RET/APP/2015(Revised)/NOTES(Revised)/(Revised again)/English or AB/CB/FL/RET/APP/2015(Revised)/NOTES(Revised)/(Revised again)/Welsh, as appropriate).
Once that has been received in triplicate, and the appropriate fee paid, your application for an AB/CB/FL/RET/SUBMISSION can be considered. If approved, you will be sent the said form which, again, needs to completed in triplicate and submitted with the appropriate fee.
If that submission is approved your AB status will then show 'flounced'.