The woman in Wales explanation:
Just before Grace was shot, Tommy was told that the sapphire she was wearing around her neck had been cursed by a gypsy. Tommy went straight over to her and begged her to take it off. Moments later she was shot by a man who had been hired by the old Italian man to kill Tommy in revenge.
With Grace dead, Tommy was wracked with guilt. The bullet was meant for him and he'd invited it by unnecessarily provoking the old Italian man. So, wanting to feel a little less guilty, he took the sapphire to a gypsy and basically asked him to confirm that it was cursed to him. That way, Grace's death would be a little less Tommy's fault.
The gypsy realised what Tommy needed to hear, so she said the words, even though she didn't think the sapphire was cursed and Tommy doesn't believe in all the woo stuff anyway. However, he was willing to pretend to himself that he believed it so that he could go away, feeling a little less guilty over grace's death. As a reward, for helping him feel better, he let the gypsy woman keep the sapphire.
Afterwards, Tommy asked the gypsy man who took him in the caravan to see the gypsy to drop him at the station, and he advised returning to the gypsy camp that evening as they'd be having a party to celebrate their new found wealth.