Like many of William's gifts of jewellery to Kate, the one he gave her to celebrate their third wedding anniversary had special links to his mother. Diana always wore a Cartier watch and gifted William with a specially engraved Cartier timepiece for one of his birthdays. In turn, William selected for Kate the Ballon Bleu de Cartier watch, which is set with a tiny sapphire — the perfect counterpoint to her engagement ring.