Delete rows that contain duplicate data in one column

I am trying to delete rows (with macro) that contain duplicate data in a specific column.

So I may have:


John Smith 01/01/1990 Ref:111
Jane Smith 02/02/1990 Ref:123
John Smith 00/00/0000 Ref:111


If the ref is the same then the whole row should be deleted. The rest of the row will not be the same. So the result would be:

John Smith 01/01/1990 Ref:111
Jane Smith 02/02/1990 Ref:123

Thanks.