Unable to delete Time Machine backup from old MacBook Pro
I have a new MacBook Pro that I have set up with Time Machine on an external HD which I had used for My old iMac. Now I can't back up the MBP anymore. The disk is full because it still contains the iMac backups. I didn't want to completely erase the HD until I was sure I had everything I needed set up on the MacBook. Now I want to delete the old backups from the iMac but can't. I get this message:
The operation can't be completed because some items had to be skipped. For each item, choose File > Get Info, make sure
"Locked" is deselected, and then check the Sharing & Permissions section. When you are sure the items are unlocked and not designated as Read Only or No Access, try again.
Locked is not checked and greyed out, I have set everything to Read & Write but still get the message.
Is there any way to delete the old backup without having to completely erase the HD, start over, and loose the MBP backups
[Re-Titled by Moderator]
MacBook Pro (M4)