In the Harley Quin short story The World's End, Alec Gerard is a playwright and the fiance of Naomi Carlton Smith. About a year before the events in the story, he had been accused of stealing an opal from an actress Rosina Nunn.
Gerard had come to Rosina's rooms to discuss one of his plays Rachel's Children which had a part in it for Miss Nunn. When he left, Rosina's opal was found to be missing. The jewel was not found on him but the empty case was found in his rooms. Moreover, he was able to pay large sums into his bank the next day. He explained that these were winnings from horseracing bets but he wasn't able to produce the friends who had placed the bets for him. Gerard had also been in Australia and so apparently knew the value of opals. He was convicted and was still serving a jail sentence at the time of the story.