At a mayoral hustings last week at St James's Piccadilly, Mr Johnson declared that he banned the ads on London buses by Christian groups, Anglican Mainstream and Core Issues Trust, because "the backlash would be so intense it would not have been in the interest of Christian people in this city".

His initial stated reason for banning the posters was his desire to protect Londoners from being exposed to the suggestion of gay therapy: "London is one of the most tolerant cities in the world and intolerant of intolerance. It is clearly offensive to suggest being gay is an illness someone recovers from and I am not prepared to have that suggestion driven around London on our buses."

Whilst his latest reason at the hustings does not contradict his earlier one, it is a significant development. It emits an even stronger whiff of democratic putrefaction.

What 'backlash' exactly against Christians is Mr Johnson afraid of? Is he concerned that the bus ads would have unleashed violent disorder against the Christian community? Church services disrupted? Vicars jostled? Or worse?

And a backlash by whom? Gay stormtroopers?

Or was he worried that Christians might get upset by people disagreeing with the idea of gay conversion?

Was he concerned that liberal Christians might get tarred with the gay therapy brush?

Does Mr Johnson think Christians, whether biblically conservative or liberal, are so feeble-minded that they cannot politely argue back or correct a misrepresentation?

Morever, has he forgotten that the New Testament teaches Christians to expect persecution? "If the world hates you, know that it has hated me before it hated you. If you were of the world, the world would love its own; but because you are not of the world, but I chose you out of the world, therefore the world hates you," John Gospel's records the Lord Jesus Christ as saying to his disciples (15v18-19 - RSV).

The threat of disorder is a time-worn excuse for suspending freedom of debate and of voluntary association.

Whilst there is every reason to believe that Mr Johnson does not desire the collapse of UK democracy and is sincere in his concern for the Christian community, his 'backlash' rationale for his gay conversion ads ban has an unfortunate ideological past. Was not protection against the threat of violent disorder used as an excuse by those wishing to undermine the Weimar democracy in Germany in the 1920s? Was it not also used as a pretext for bolstering the Stalinist dictatorship in the Soviet Union in the 1920s?

It should not be assumed that because democracy in the UK evolved, its decline will be slow. It could collapse very quickly. Unless radical action is taken to treat the dry-rot in UK democracy, its collapse may not take more than a decade.

That is the disturbing cultural context in which FCA leaders meet to plan the way forward for orthodox Anglican mission and ministry.

Julian Mann is vicar of the Parish Church of the Ascension, Oughtibridge, South Yorkshire - www.oughtibridgechurch.org.uk