https://www.slab.org.uk/guidance/taking-defence-statements-in-high-court-cases-2/
Under the Crown Practice Statement on disclosure of statements and productions, the Crown must give the defence
If you are aware of the identity of Crown witnesses material to the defence and you can show urgency, you may take statements from those witnesses before receiving the copy Crown statements. We would normally expect you to wait until the 28 days pass.
Once you have seen the copy Crown statements or if, after 28 days, the Crown has not produced copy statements, you can take statements (subject to the guidance set out in this pamphlet).
These arrangements also apply where the Crown informs you that the provision of copy statements will be delayed for a specific period beyond the 28 days.
You do not need our prior approval to take statements from a Crown witness considered to be material to the defence, unless this could involve unusual work or unusually large expenditure.