During automatic update: could not initialise the package information

[James Baber]

"An unresolvable problem occurred while initialising the package information.

Please report this bug for the 'update-manager' package and try to include the following error message:
E:can not open /var/lib/apt/lists/gb.archive.ubuntu.com_ubuntu_dists_focal-backports_InRelease - fopen (13: Permission denied), E:The package lists or status file could not be parsed or opened."

Ubuntu 20.04.2 LTS
update-manager 1:20.04.10.6
This occurred during an automatic update that occurred after a wake from sleep.
The error appeared in a popup window named "Software Updater"

Upon opening this package again, after a brief scan, it says "Failed to download repository information. Check your Internet connection." Yet a ping to google.com returns successfully.