System Image Restore Points won't delete

[jan18]

In System Restore I have three ‘System Image Restore Points’ classification type ‘Backup’ All three go back to 2014 and are of no use to me anymore. I have tried to Delete them using the Delete button in System Restore but they always remain listed even after all my other Restore Points have gone.

Anyone know how I can delete these three images.

Thanks

Jan