The ad, backed by the Core Issues Trust, which stated: 'Not gay! Ex-gay, post-gay and proud. Get over it!' The mayor of London , Boris Johnson , intervened to prevent a Christian advertising campaign from promoting the idea that gay people can be converted to heterosexuality. Just days before the posters were due to appear on buses in the capital, Johnson ordered his transport chiefs to pull the adverts booked by two conservative Anglican groups following outrage among gay campaigners and politicians saying that they were homophobic. The adverts were booked on behalf of the Core Issues Trust whose leader, Mike Davidson, believes "homoerotic behaviour is sinful". His charity funds "reparative therapy" for gay Christians, which it claims can "develop their heterosexual potential". The campaign was also backed by Anglican Mainstream, a worldwide orthodox Anglican group whose supporters have equated homosexuality with alcoholism. The advert was due to say: "Not gay! Post-gay, ex-gay and proud. Get over it!" Johnson, who contacted the Guardian to announce he was stopping the adverts within two hours of their contents becoming public, said: "London is one of the most tolerant cities in the world and intolerant of intolerance. It is clearly offensive to suggest that being gay is an illness that someone recovers from and I am not prepared to have that suggestion driven around London on our buses." His main rival in next month's mayoral election, Ken Livingstone, said Johnson should never have allowed the adverts to be booked. "London is going backwards