Same-sex couples getting married in England and Wales will have to wait until Saturday 29 March to hold their ceremony but a quirk in the law – first reported by BuzzFeed – means couples who married overseas will have their unions automatically recognised from 13 March onwards.

This includes Celia Kitzinger and Sue Wilkinson, two university professors who married in Canada in 2003 and spent the last decade campaigning for their partnership to be recognised in Britain. On Thursday, thanks to the government's decision to bring forward the Marriage (Same Sex Couples) Act, that day will finally come.

"It's like being turned into a pumpkin on the stroke of midnight," Celia told BuzzFeed. "We'll be sitting there in bed with a bottle of champagne and at the stroke of midnight we'll turn into a married couple. We're going away to a hotel, having a nice meal and the at midnight we'll be wife and wife again!"

There's no paperwork and no formal process. But when the day switches from Wednesday to Thursday all overseas same-sex marriages will at last be legally recognised.

And for the first time there will be couples in Britain who are able to call themselves husband and husband, or wife and wife in the eyes of the law.