It was quite reasonable to suppose therefore that Sixtus would have his alert eyes on Isabella and Ferdinand and would seek some means of curbing their power. How could this be done with greater effect than by installing the Inquisition – an institution which was apart from the state and had its roots in Rome? The Inquisition could grow up side by side with the state, gradually usurping more and more of its power. It could be equivalent to a measure of Roman rule in Spain.

Isabella looked with grateful affection at the Cardinal, who had been thinking on the same lines and who saw the issues at stake as clearly as she did herself.

‘I know Your Highness will agree with me that we must be continually watchful of the power of Rome. Here in Castile Your Highness is supreme. It is my urgent desire that you should remain so.’

‘You are right as usual,’ answered Isabella. ‘But I am disturbed that some of my subjects should revile the Christian faith.’

The Cardinal was thoughtful. In his heart – although this was something he could never explain to Isabella, for he knew she would never understand him – he believed in taking his religion lightly. He was aware that belief – to be real belief – must be free. It was something which could not be forced. This was contrary to the accepted notion, he was fully aware, and for this reason he must keep his thoughts to himself. He wished life to be comfortably pleasant and, above all, dignified. The Inquisition in Aragon, Valencia and Catalonia was, he realised, at this stage a lethargic institution. Its officers lived easily and did not much concern themselves with the finding of heretics. If such were discovered they could, no doubt, by the means of a little bribery and diplomacy, escape disaster.

But when he thought of this earnest young Queen who, by her single-minded purpose and strict punishment of all offenders, had changed a state of anarchy into one of ever-growing law and order, he could imagine what such a new and terrifying institution as the Inquisition could become under the sway of Isabella and such men as Tomas de Torquemada, whom it was almost certain, Isabella would nominate – perhaps with himself – as her chief adviser if she should establish the Inquisition in Castile.

Isabella and Torquemada were stern with themselves; they would be more dreadfully so with others.

To a man who loved luxury, who cared for good living, who was devoted to the study of literature and enjoyed translating Ovid, Sallust and Virgil into verse, the thought of forcing opinions on men who were reluctant to receive them, and would only do so under threat of torture and death, was abhorrent.

Cardinal Mendoza would have enjoyed calling to his presence those men of different opinion, discussing their views, conceding a point, setting forth his own views. To force his opinions on others was nauseating to a man of his culture and tolerance. As for the thought of torture, it disgusted him.

This he could not explain to Isabella. He admired Isabella. She was shrewd; she was earnest; she was determined to do what was right. But, in the Cardinal’s opinion, she was uneducated; and he deplored her lack of education, which had resulted in a narrow mind and a bigotry which prevented her from meeting the Cardinal on his own intellectual level.

The Cardinal was going to fight against the installation of the Inquisition with certain enthusiasm. He could not, however, bring to bear the fervour of a Torquemada, for he was not of the same fervent nature. But he would certainly attempt to lead Isabella away from that line of action.

He said: ‘Highness, let us give a great deal of thought to this matter. Before we decide to bring in the Inquisitors, let us warn the people of Seville that they place themselves in danger by denying the faith.’

Isabella nodded. ‘We will prepare a manifesto . . . a special catechism in which we will explain the duties of a true Christian. This could be set up in all churches in Seville and preached from all pulpits.’

‘Those who do not conform,’ said the Cardinal, ‘will be threatened with the fires of hell.’

‘It may well be,’ said Isabella, ‘that this will be enough to turn these men and women of Seville from their evil ways.’

‘Let us pray that it will serve,’ said the Cardinal. ‘Is it Your Highness’s wish that I should prepare this catechism?’

‘None could do it so well, I am sure,’ said Isabella.

The Cardinal withdrew, well pleased. He had – for the time at least – foiled the attempt of the Dominicans to install the Inquisition in Castile. Now he would produce his catechism, and he hoped that it would bring about the required effect.

Shortly afterwards Mendoza’s Catecismo de la Doctrina Cristiana was being widely circulated throughout the erring town of Seville.

When Torquemada heard that Mendoza’s Catecismo was being circulated in Seville he laughed aloud, and laughter was something he rarely indulged in. But this laughter was scornful and ironical.

‘There is a great deal you have to learn about the wickedness of human nature, Cardinal Mendozal!’ he murmured to himself.

Torquemada was sure that the heretics of Seville would pretend to study the catechism; they would feign belief in the Christian faith; then they would creep away and jeer at Mendoza, at Isabella, at all good Christians while they practised their Jewish rites in secret.

‘This is not the way to cleanse Seville!’ cried Torquemada; and he was on his knees asking for Divine help, imploring the Virgin to intercede for him, that he might be given the power to cleanse not only Seville but the whole of Castile of the taint of heresy.

In time, he told himself, understanding will dawn on the Queen – even on the Cardinal who, though a good Catholic himself, leads a far from virtuous life. Scented linen, frequent baths, amours . . . indulgence in the sensuous enjoyment of music and literature! The Cardinal would on his deathbed have to ask remission of many sins.

Torquemada embraced himself, pressing his arms round his torso so that the hair shirt came into even more painful contact with his long-suffering body. Secretly he thanked God and the saints that he was not as other men.

It seemed to him then that he had a glimmer of the Divine will. His time would come. The Cardinal would fail, and into the hands of Torquemada would be placed the task of bringing Castile to repentance.

Until then he might concern himself with the building of the monastery of St Thomas. So to Avila he travelled with a good conscience. He was sure that soon he would receive the call to desert pleasure for duty.

Isabella had journeyed to Seville.

It had been the custom of the Kings of Castile to sit in the great hall of the Alcazar and pronounce judgement on offenders who were brought before them.

Each day Isabella attended in the great hall. Occasionally Ferdinand accompanied her and they sat side by side administering justice.

These sessions were conducted in a ceremonial manner, and Isabella was sumptuously dressed for the purpose. She took little delight in fine clothes, but was always ready to see the need for splendour. It was imperative that she be recognised in this turbulent city as the great Queen of Castile; and in this place, where the inhabitants had lived among the remains of Moorish splendours, it was necessary to impress them with her own grandeur.

Isabella proved herself to be a stern judge.

Determined as she was to eradicate crime in her kingdom, she showed little mercy to those who were found guilty. She believed that the slightest leniency on her part might send certain of her subjects back to a life of crime, and that, she was determined, should not happen. If she could not make them reform for the love of virtue she would make them do so from the fear of dire punishment.