That momentum has also prompted greater international solidarity between groups campaigning for gay rights, according to Andy Wasley, a spokesman for the UK's Stonewall charity.

CNN: Opinion: Why the fuss about gay marriage?

Wasley said that growing recognition and awareness of the principles of universal human rights through institutions such as the United Nations and the European Union had also served the cause of gay rights campaigners.

CNN: Opinion: Why the fuss about gay marriage?

"We work together with organisations worldwide to help challenge homophobia, and we've provided advice to campaigners in countries like Croatia and Slovakia, which are looking to learn from the progress we've made on equality in Britain, " Wasley told CNN.

CNN: Opinion: Why the fuss about gay marriage?

Wasley also highlights continuing casual homophobia in the UK, citing Stonewall research suggesting more than half of gay, lesbian and bisexual young people have been bullied at school and Home Office records of 4, 200 homophobic hate crimes in England and Wales last year.

CNN: Opinion: Why the fuss about gay marriage?