The strict and uncompromising nature of his extremist Gregorianism challenged and weakened his partnership and alliance with the Holy See in the last decade of his archiepiscopal tenure, which coincided with the pontificate of Pope Alexander III.

[8] Historian Ubul Kállay rejected the aforementioned theories and argued Apa and Lucas were the sons of Alexius, a Ban of Slavonia during the reign of Stephen II of Hungary.

[9] "I saw at Paris, in the school of Master Gerard la Pucelle, Luke of Hungary, a man of honour and great culture, who shared his table with the poor in such a way that they seemed invited guests, not seekers of alms.

[13] Among his fellow pupils was supposedly English chronicler Walter Map (Gualterius Mappus), who recalled Lucas in his only surviving work De nugis curialium.

According to Györffy, they did not know each other personally (Thomas Becket was a secretary of Theobald of Bec by the time Lucas resided in Paris), but they knew about each other through mutual acquaintances and used similar ecclesiastical tools to defend their interests against the secular royal power.

Due to a lack of sources, there is no record of Lucas' activity or function as the Bishop of Eger; his name only appears in the list of dignitaries of the various royal charters issued by Géza II.

[18] In 1157 political unrest occurred in Hungary; chronicler Rahewin records that King Géza II's youngest brother, Stephen, began conspiring with their ambitious uncle, Beloš, and other lords against the monarch.

Géza II expelled his rebellious brother and sentenced him to death, while Beloš lost his influence over the royal court and fled Hungary in the latter half of the year.

[20] After their failed rebellion, Géza II's two brothers, Ladislaus and Stephen sought refuge in the Byzantine Empire by 1160, where they found shelter in the court of Emperor Manuel I Komnenos at Constantinople.

[11] Literary historian János Győry suggested that Lucas sympathized with the heretic movements prevalent in the region – Albigensians, Patarenes and Bogomils, but the majority of scholars do not share this fringe theory.

[9][30] Initially, Géza II supported the efforts of Frederick Barbarossa against the pro-papal Italian communes (that were later known collectively as the Lombard League), and even sent Hungarian auxiliary troops to accompany the Holy Roman Emperor to Italy between 1158 and 1160.

[32] A letter from Lucas to his ally, Eberhard, Archbishop of Salzburg, who was the leading pro-Alexander figure in the Holy Roman Empire, revealed his influence carried significant weight with Géza II when he changed the direction of his foreign policy.

[36] Géza II and Pope Alexander III's envoy, papal legate Pietro di Miso signed a concordat in the summer of 1161 that Lucas mediated.

[39] The decretal, which later became part of Decretales Gregorii IX (or Liber extra), reflects Lucas' rigid individuality, excessive strictness, and extreme Gregorian views which characterized his reign as Archbishop of Esztergom.

[5][22][40] 18th-century historian Miklós Schmitth notes that Lucas successfully recovered the stolen gems of the late Martyrius from the thief Jordanus immediately after being elected as archbishop.

[41] According to a royal charter supposedly issued by Stephen III, Géza II ordered Ded of Vác and Chama of Eger to rededicate the Szentjobb Abbey (present-day Sâniob in Romania) with Lucas' consent.

He was immediately visited with anathema by Luke, whom he forthwith urged with dreadful threats and even with the menace of a naked sword to absolve him; but, receiving for an answer scorn and like-wise excommunication, he thrust the Archbishop violently into prison and compelled the suspended churches to disregard the interdict.

[47] According to Map's De nugis curialium, the new monarch tried to intimidate and persuade the prelate to his side, but Lucas remained steadfast and strongly condemned his controversial accession to the Hungarian throne.

Lucas' political interests conflicted with Pope Alexander's, who maintained a moderately good relationship with the courts of Ladislaus II and Emperor Manuel on account of the constant threat of Barbarossa's anti-papal policy.

Church historian József Török argues Lucas saw the consistent and exclusive application of the ancient custom of primogeniture as the pledge of the stability of the kingdom, which was endangered by the ambitions of Ladislaus and Stephen.

[65] However the pope supported Stephen III against Lucas when the archbishop attempted to hinder the consecration of the king's protégé, Andrew, Bishop-elect of Győr, because of his allegedly non-canonical election.

[66] "If you want to listen diligently and carefully consider, how much We have always put [our trust] in you, and how We supported you, to Our great shame, also by breaking the truth, you will understand, not because of Our harshness, but because of the quality of your merits that We are denying the solemn consolation of the Apostolic Blessing from you.

Because you can remember enough how much you were impenitent and rebellious towards us [...] how much shame and injustice, how much contempt and insult We were forced to endure from you in the matter of the said Archbishop [Andrew], who [...] was excommunicated and declared oath-breaker by you despite Our ban.

Béla, who lived in Constantinople since 1163 and was the former designated heir of the Byzantine Empire, arrived in Hungary with his wife Agnes of Antioch in Székesfehérvár in late April or early May.

[79] Historian Pál Engel observed Lucas' "anxiety proved to be wholly unjustified", as Béla III governed Hungary as an independent monarch and excluded the neighboring empire's influence beyond its borders throughout his reign.

[83] Lucas charged Andrew with the unlawful domination of priests and clergymen of the royal churches, which were traditionally placed under the territorial authority of the Archdiocese of Esztergom.

[78][85] In his harshly-worded letter sent to Hungary in March 1179, Pope Alexander listed Lucas' past "sins" in detail since the rule of Stephen III and threatened to excommunicate him if he maintained the punishment he imposed on Andrew.

[84] According to Italian historian Odorico Raynaldi, Lucas died as an "eminent moral priest", who cured sick people of their various illnesses, honouring him as a saint.

[89] Upon his request, Pope Gregory IX entrusted Bulcsú Lád, Bishop of Csanád and two other clergymen on 28 August 1231 to conduct an investigation and send their report to Rome.

[88] After receiving the report and the letter in support of Andrew, the pope ordered papal legate Giacomo di Pecorari on 17 February 1233 to deal with the canonisation issue among other matters.