The ramparts of the Portuguese Castle of the Moors – “Castelo dos Mouros” – fell to the Christians of the Second Crusade in 1147, a bunch of thieves and drunkards, according to local reports, which included a fair number of Brits. There’s a story that a huge fortune in gold and coins still lies beneath the castle’s broken and much-restored walls, hidden there by the Moors when Afonso Henriques’ thugs were climbing the hills above Sintra. My guess is there’s none. Our relations with the Muslims have always revolved, it seems to me, around money and jealousy. Besides, the Crusaders looted their way across Lisbon – after a solemn agreement with the King that they could do so – and then massacred and raped their way through the panic-stricken Muslim population.

It was the only victory the Second Crusade achieved – things went badly wrong for it in the real Middle East. After that – and the 15th-century expulsion of the Muslims – Portugal’s conflict with the region was economic rather than military, trying to grab the Indian trade routes from Yemeni Arabs. When Vasco da Gama “discovered” India and reached Calicut (Kozhikode) on 20 May 1498 – this story comes from Warwick Ball’s Out of Arabia – he was greeted by an Arab from Tunisia with the words “May the devil take you! What brought you here?”

But that was about it. Only well over four hundred years later do we find the Christian nationalist dictator Antonio de Oliveira Salazar – who kept Portugal neutral in the Second World War and thus preserved its “oldest ally” relationship with Britain – declaring that in the 15th and 16th centuries, his country had defended “Christian civilisation against Islam”, a remark that might have come from Viktor Orban of Hungary today. It was historical rubbish, and may be the reason why there is no anti-Muslim ideology in Portugal. If you visit the enormous tomb of Da Gama in the Jeronimos Monastery church at Belem, the catafalque carries two magnificent sculptures of medieval merchant ships but no reference to Muslims. Da Gama’s sword is sheathed under stone drapery. The Manueline monastery cloisters which I walked through next door, however, are dripping with Arab-style archways and Arabesque tiles (which you might find today in Algeria and Tunisia).

The Department of Home Truths, a Fiskian institution I have found it necessary to deploy around the Middle East, would point out, of course, that Portugal visited its violence and ethnic cleansing and racism and slavery not upon the Middle East but upon the peoples of Africa, where later wars in its very own colonial possessions – especially Angola and Mozambique – helped to bring down the pseudo-fascist regime of Marcelo Caetano, Salazar’s successor, in 1975.

The Arabs, however, were regarded as exotic and educated peoples whose own culture was never erased from the streets of Portugal’s cities. The museum commemorating prisoners of 20th-century dictatorship is located in an original Moorish building in Lisbon called Aljube, which in Arabic means, “Street of the Watercourse”. It can also mean “prison” – which is what it was under Salazar. Iberian languages, I should add, are equally strewn with Arabic. The warrior El Campeador, Rodrigo Diaz de Vivar (of Charlton Heston fame), is best known to us by his Arabic nom-de-guerre, “as Sayyid” – El Cid (“the Lord”).

Nowhere can present day connections between the Muslim and European past be more perfectly illustrated than in Lisbon’s Calouste Gulbenkian Museum in the northern suburbs of Lisbon. Old Gulbenkian, the richest Armenian of his time, the original “Mr Five Per Cent” of oil earnings, was an extraordinary philanthropist of his time, his foundation even trying to bridge the insurmountable gap between the Armenian peoples and their genocider Turkish fellow citizens after 1915. This may be why the short biography of the man available at the Lisbon institution refers to the Armenian genocide – disgracefully – as merely “the tragic events”.

But the museum displays Muslim/Arab art scarcely a couple of rooms from Dutch old masters, Thomas Gainsborough’s Mrs Lowndes-Stone and a couple of Turners. A Syrian Mamluk mosque lamp and an Armenian illuminated bible stand only a few metres from Renoir’s Portrait of Madame Monet. A new exhibition looks at botanical knowledge shared by Europe with the Mughal empire of Shah Jahan.

But there is one majestic volume among the Muslim books, a 16th-century Iranian copy of the 14th-century poetry of Hafiz, the 400-year-old Safavid scholar’s handwriting swooping delicately across an open page of the volume – but a text, alas, untranslated, and thus rendered as art rather than literature. But here, abbreviated and forced into English, is what some of the words say: “If, by good fortune, I can obtain the dust from my beloved’s foot, above my eyes I will inscribe a line. If her moth searched for my soul like a candle, I would give up my soul at that very moment … After death, even the wind will not be able to take my dust away from your door.”

The lines are not unlike the more ascetic, broken, almost negative verse of that undeniably finest of modern Portuguese poets, Fernando Pessoa, who reminds his devotees of both Joyce and Samuel Beckett:

“In the dead afternoon’s gold more –

The no-place gold dust of late day

Which is sauntering past my door

And will not stay –

In the silence, still touched with gold,

Of the woods’ green ending, I see

The memory. You were fair of old

And are in me…

Though you’re not there, your memory is

And, you not anyone, your look.

I shake as you come like a breeze

And I mourn some good…”

This is Jonathan Griffin’s translation from the Portuguese, but Pessoa’s work immediately prompted a Muslim visitor to Lisbon to remark to me how similar it was to the 11th-century Persian poetry of Omar Khayyam, whose Rubaiyat was itself translated (though not very well) by the English poet Edward FitzGerald. Pessoa spoke fluent English.

It comes as no surprise, therefore, to discover that Pessoa not only read and took copious notes on the Rubaiyat all over the title page of his copy of FitzGerald’s work, but became almost obsessed by Arab philosophers, including the 11th-century Arab-Andalusian poet al-Mu’tamid. And he condemned the Middle Ages Arab expulsion from the Iberian peninsula. Thanks to the work of Italian scholar Fabrizio Boscaglia and Brazilian researcher Marcia Feitosa, we find Pessoa espousing “our [Portuguese] great Arab tradition – of tolerance and free civilisation. It is in the manner in which we are the keepers of the Arab spirit in Europe that we will have a distinct individuality… Let us revenge the defeat inflicted by those from the North to our Arab ancestors. Let us redeem the crime we committed when we expelled from the peninsula the Arabs that civilised it.”