On the cobblestones outside the great 8th century mosque in Córdoba, once the largest mosque in the western world, Mansur Escudero, a Spanish convert to Islam, unfolds his prayer mat and kneels down to pray.

Muslims are not allowed to pray inside. The Roman Catholic Church, custodian of the building since the 13th century, says it would “confuse” Christians to see Muslims worshipping there. Mr Escudero has lobbied the Vatican to transform the Córdoba mosque into an ecumenical place of worship, – “a symbol of religious tolerance and co-existence,” he says – but his campaign has not met with success.