Can't Delete a Field from a Form

Can't Delete a Field from a Form

I'm trying to delete a couple of fields from a form, but when I try to delete the field, then I get a message saying that "This field is referred in the following places. Please remove them and then delete this field." and it gives a list of Views.

However, the field is not included in any of the Views listed. The only connection I can see is that the Views are all based on the Form that contains the field I would like to delete.

Can anyone suggest how I can get these fields deleted from the form?

Thanks,
David