Deleting all but one record from the same day

Thanks Marcol, you've solved another problem for me

I had a bit of a job with removing the unwanted records. I wasn't sure about filtering for blanks so ended up using column E to check column D for '1' and entering "Delete" if it didn't appear. I then replaced column C with the contents of E, copied cols A, B and C to a new workbook, replaced "Delete" with nothing, sorted on C and deleted all the rows where C was empty.

I had to go through this process because it seemed the contents of D were really slowing the workbook down. I've got a pretty decent spec (Core i5, 8Gb Ram, SSD) but a sort I started at 8pm last night hadn't finished by the time I went to bed. And when I woke up, the sort said it had finished but nothing on the workbook had changed . Even trying to delete the contents of column D took over an hour with no discernible progress.

Anyway, I've got the results I wanted. Thank you.