The advertising campaign was conducted by the lesbian, gay and bisexual charity Stonewall to coincide with the government consultation on proposals to extend the legal form of marriage to same-sex couples.
The uncompromising slogan was originally launched by the charity in November 2007 to tackle homophobic bullying in schools. It has since been used in a number of campaigns. Laura Doughty, deputy chief executive of Stonewall, says: "The message is still very relevant and can be adapted for different audiences. Given the profile of equal marriage, it seemed really appropriate to use for this campaign. Each time we have used the message we have aimed to reach different audiences with it and to attract new supporters."
The campaign's objective was to promote awareness of equal rights issues, get people talking and encourage participation in the consultation by linking to Stonewall's equal marriage website. The buses were seen by an estimated 90 per cent of the adult population in London.
"Buses are a good medium because they ensure a wide range of people see them," says Doughty. "As with other forms of outdoor advertising, it is not self-selecting." Stonewall chose to run the adverts only in London because it wanted to reach Westminster and opinion formers, and to encourage a range of people to participate in the consultation. And a wider geographical campaign would have cost too much.
To extend the campaign's reach, the charity asked supporters to tweet pictures of the buses carrying the advert using the hashtag #equalmarriage, or to post them on its newly launched Facebook page. A prize was offered to the supplier of the best picture each week.
The simple campaign won national and international coverage - including on Channel 4 News and in the 'pink' media. It made the front cover of a magazine in Hungary and drew interest from Russia, Israel and France.
"We feel it was very successful," says Doughty. "We have had responses from people with gay children, teachers and people who are active in churches. But the success is not purely about numbers - it's getting the message heard."
Lara Samuels, Director, The Communications Hub
If the Stonewall campaign intended to turn heads, it certainly succeeded. The only trouble is, it might have been the wrong sorts of heads.
As reported in the media at the time, the Core Issues Trust played on the creative element, adapting it to promote some of its own fairly unpalatable and homophobic views on similar bus sides, although London mayor Boris Johnson pulled these adverts before they appeared.
Perhaps any publicity is good publicity. After all, Stonewall's campaign made a bold statement, got good coverage and lots of people have heard about it.
But has it really changed anyone's views? To make inroads with audiences who aren't yet on the same wavelength - like the Core Issues Trust, for instance - maybe a different tack is needed.
Total: 6 out of 10