✔ 最佳答案
What was the cause want to amend grant of probate?
Change the grant of administrator or the other terms inside the grant?
you may write letter and affirmation in support to probate's registry for made application to obtain leave to amend the same (of course, the original grant must annexed).
(Full details for the application to amend should made enquries to probate's registry directly).
(My opinion is not legal opinion)
(legal opinion should be obtain from a professional solicitors).