Deleting previous recipients in iCal

I understand from your question that old or redundant email addresses might be appearing when you select people to invite to an event in Calendar.

Apple's Calendar does not have a list of previous recipients to edit or delete. Instead, you will need to go to the Mail application and, if on a Mac (what device are you using?) select Window > Previous recipients. Search for the address you wish to delete, select it, then choose the option at the bottom of the panel which says 'Remove from List'.

Also, launch your Contacts app and see if your contact has this address and if so delete it.

This should stop it appearing when you use Calendar.

Thanks for the suggestions David. I am using a Mac with the latest OS. I've done these previously, but checked them again. The email address does not show up in the mail previous recipients nor in my contacts.

I should have been clearer in the problem description. The problem is not showing up on my Mac, but on my iPad and iPhone. Both are running the latest iOS.