Imagine a return to a world where people of different ethnic background or religion were only allowed to travel on separate buses or were treated in different hospital wards.
Imagine a government justifying itself by saying that, well, those people are still offered travelling facilities and can still be treated if they're sick, overlooking the simple fact that different means and separate channels can only suggest inferior status before the law.
The thing is, that world is with us in today's Britain.
Except that the victims of discrimination are not ethnic or religious minorities, but sexual ones.
If you are gay or lesbian and you wish to get married, the law actively prevents you from doing so. You are offered something different called "civil partnerships" - but the law keeps it as the exclusive preserve of same-sex couples.
The Equal Love campaign, launched last month by the human rights organisation Outrage!, is trying to put an end to this pointless and unjustified discrimination.
When last month a number of same sex-couples applied for civil marriages in London, Northampton, Hampshire and Greenwich, they were all turned away by Register Office staff.
But if more evidence was needed about the absurdity of Britain's sexual apartheid, a number of heterosexual couples were also rejected when they too applied for "civil partnerships". The current law doesn't let them. One bus if you're straight, another if you're not.
Civil Partnerships were brought in by the Labour government in 2004. Although an admirable step in the right direction, especially if compared to the previous regime of total prohibition, the current law is still discriminating on the ground of sexual orientation - a blatant breach of the Human Rights Act.
Yet a number of countries around the world have ended sexual apartheid. Canada, Sweden, Belgium, Argentina, Spain, Norway and the Netherlands are only some of the places where the law doesn't meddle with marriage and sexual preferences.
In an opinion poll published last year by the Times, 61% of the British public agree that gay people should have an equal right to get married, not just civil partnerships, further demonstration that the current two-tier regime is absolutely pointless.
Two out of three party leaders have also come out in favour of an end to the discrimination. Both Ed Miliband and Nick Clegg have openly said they would vote in favour of a change in legislation.
As for the other one, still nowt. Could it be David Cameron's mark of respect for his Party's history of endless anti-gay discrimination?
Click here to find out more about the Equal Love campaign.