LONDON—Following the House of Commons’ passage Tuesday of a bill that paves the way for same-sex marriage in Britain, Queen Elizabeth II publicly announced her plans to marry her longtime partner, 63-year-old Denise Whitelock, as soon as the law goes into effect. “After more than 30 years of sharing a committed and loving partnership, I am absolutely thrilled that Denise and I are finally able to seal our union in marriage,” said the reigning British monarch in a press release, speaking on behalf of her partner, a retired dog breeder, with whom she lives part-time in a Kensington Garden flat. “Marriage is something we’ve both wanted for a very long time, but never had an opportunity to pursue because of the unequal and antiquated marriage laws of this country. We’re delighted that the government finally took this important step forward, and we couldn’t be happier to announce our official engagement.” The Queen also informed members of the press that, as this was her second marriage, she and Denise had decided to hold a low-key ceremony with close friends and family.