This generates STDERR, which will in turn generate an email each day that cron runs it, because `govuk-backup` isn't allowed to traverse into the `lost+found` directory:
```
dcarley@offsite-backup-1:~$ sudo -u govuk-backup find /srv/backup-data -type f -mtime +30 >/dev/null
find: `/srv/backup-data/lost+found': Permission denied
```
We can prevent that by excluding the directory:
```
find /srv/backup-data -not \( -path /srv/backup-data/lost+found -prune \) -type f -mtime +30
```
(I've omitted `-delete` from both just to test)