Making an external drive Read-Writeable

Hi,

I recently had to rebuild / reinstall my Mac after an upgrade to Big Sur failed and left the disk corrupt.

I reinstalled the OS and recreated all the settings on the OS including recreating the main login account on the OS.

I used to have an external drive attached (mounted as NTFS) which stores all my photos and documents.

That drive is re-mounted as before but it's Read-only and I can't make it writeable despite the permissions seeming to show that it is.

Any ideas please