Buyer requesting a return because it was late although posted on time

[oliver27bailey]

Hi my buyer is requesting a return and full refund because although I posted the item on time and have proof of postage and of delivery it was too late fir her event (dress) will I have to agree the return? It doesn't seem fair as I kept up my side of the transaction and it is total nail who are at fault.  Can't claim from Royal Mail as it arrived on day 9 

[plpmr]

Unless things have changed - if it arrived later than the last estimated delivery date they can open a not as described case.