There is no proof that Henry Sinclair accompanied King Peter of Cyprus on the ill-fated attack on Alexandria in 1365 except that a group of Scottish Knights had assembled at Venice with other "Crusaders" and it was assumed that Henry may have been amongst them. 400 ships left the Arsenale in Venice to plunder Alexandria. They travelled via Cyprus.

Henry had also met King Peter, King Peter's Chancellor, Philppe de Mezieres and Carlo Zeno in Copenhagen in 1364 when they were touring the Northern Capitals of Europe in an attempt to raise funds for the Crusade. This was not unusual. The Scandinavian countries were always a good source for fighting men (probably because they had nothing better to do) and even Orkney provided a contingent. All this is documented.

As Henry 'disappeared' from Copenhagen (where he was Ambassador) at that time, it was assumed he may have gone along with the recruiting party but, I repeat, this is pure assumption.

He also became known as Henry 'the Holy' St Clair - an appellation which was frequently given to those who had taken part in a Crusade just as, today, Muslims who have made the pilgrimage to Mecca are referred to as "Al Haji" - the Holy. This, too, was taken as an indication that Henry might have taken part in a Holy Crusade but, as Laurel frequently alludes, there was very little that was Holy about any of the Crusades. They were bloody affairs disguised under the name of Holy Crusades. The sacking of Alexandria was a case in point. It was wholly unjustifiable but, then. all 'religious' wars are - religion becomes an excuse for untold barbarism. The 2nd millennium will be renowned for its religious wars culminating in Kosovo, Chechnya and East Timor. Barbarism is still unchecked by those (whether Christian or Muslim) who profess to follow the path of peace.

Niven Sinclair

``King Peter I of Cyprus finally organized an expedition that in 1365 succeeded in a temporary occupation of Alexandria. After a horrible sack and massacre, the unruly crusaders returned to Cyprus with immense booty. Peter planned to return, but no European aid was forthcoming, and after his murder in 1369 a treaty of peace was signed. No further crusades set out with Jerusalem as the objective. What followed were not really crusades in the old sense but campaigns such as the crusades of Nicopolis in 1396 and Varna in 1444, whose purpose was to defend Europe against the Ottoman Turks, a new power in the East.''
— ENCYCLOPÆDIA BRITANNICA

``Peter of Lusignan, King of Cyprus, wishing to wage a good and profitable Crusade, departed with a great fleet and sacked Alexandria in Egypt. The Sultan of Cairo, Al-Ashraf Shaaban, as an act of revenge, persecuted all the Christians in his kingdom. He imprisoned sixteen Franciscans of the Holy Land. They remained in prison in Damascus for five years where they died of privations.''
— The Franciscans