Íñigo died shortly after the assassination of his overlord Sancho IV of Navarre and the subsequent takeover of Biscay, Álava, part of Guipúzcoa and La Rioja by Alfonso VI of Castile. He accepted Alfonso as his lord and his son followed suit, although after Íñigo's death the tenencia of Nájera, the most important in La Rioja, which he had held was given to García Ordóñez, husband of Urraca, sister of the deceased Navarrese king. Nevertheless, it was Lope and Diego Álvarez de Oca whom the king had swear to uphold and guarantee the fuero of Nájera which he had granted (1076).
For the loss of Nájera, Lope was compensated with the tenencias of Álava (1081) and Guipúzcoa (1082) and he was thus the first to unite the Basque provinces under one lord. The first record of his simultaneous rule in all three provinces comes from a charter of donation he made to the monastery of San Millán de la Cogolla in 1082, which he signed as "I, lord Lope Íñiguez, governing Biscay, Guipúzcoa and Álava". This concentration of political authority led to the suppression of the Diocese of Álava and the consignment of its province to the Diocese of Calahorra in 1087. In 1089 Lope received the title of count, the highest rank in the kingdom, from Alfonso. Lope's importance continued to grow, for in 1091, at his instigation, Alfonso VI donated the monastery of San Andrés de Astigarribia, which lay on the border between Biscay and Guipúzcoa, to San Millán.
Lope was a regular participant in Alfonso VI's Reconquista. He probably took part in the conquest of Toledo in 1085. Forces from Álava are known to have participated in the Battle of Sagrajas in 1086, probably under his leadership. In the spring of 1092 he probably joined with García Ordóñez in defending the Rioja from the depredations of from the exile and freebooter Rodrigo Díaz de Vivar.
Lope married Ticlo (Tecla) Díaz, daughter of a certain Diego Álvarez, possibly Diego Álvarez de Ayala, who ruled Asturias de Santillana, but more probably Diego Álvarez de Oca. Their marriage took place before 1079, when the couple made a donation to San Millán. Ticlo may have brought part of Las Encartaciones to Lope, thus uniting them permanently with Biscay. She gave birth to an heir, Diego I, named after her father. The names Diego and Lope would alternate in the heads of the family for generations. Ticlo bore four other children: Sancho, Toda (who married Lope González, who succeeded Lope in Álava), Sancha and Teresa (who married García Sánchez de Zurbano and later went on a pilgrimage to Rome). Shortly after Lope's death in 1093 Ticlo donated the monastery of Albóniga to San Millán for the good of his soul. She died towards 1104 and was buried in San Millán. Lope may also have been the father of Pedro López de Monforte.
Lord of Biscay
Diego López I de Haro
- Ego senior Lope Enneconis dominante Bizcaia et Ipuzcoa et Alaba. The title senior (modern Spanish señor) was more typical of Navarrese titulature, whereas the Castilians preferred the form dominus (modern Spanish don).
- He witnessed a royal diploma as "count Don Lope of Biscay" (Comite domno Lope Bizcaie).
- His record indicates he held non grudge against either Alfonso or García for the loss of Nájera.
- The source is a notice added in that year to a document of 1080 in the archives of San Millán. The knights Sancho Fortúnez and his nephew Sancho Ortiz, both from Álava, are known to have been at Sagrajas (Sacralias) north of Badajoz.
- This was the suggestion of Juan Antonio Llorente, based on the numerous donations the couple made in the Valle de Mena, where many of Diego's interests lay.
- Barton, 281.
- Simon Barton. The Aristocracy in Twelfth-century León and Castile. Cambridge: Cambridge University Press, 1997.
- Ghislain Baury. "Diego López 'le bon' et Diego López 'le mauvais': comment s'est construite la mémoire d'un magnat du règne d'Alphonse VIII de Castille." Berceo, 144(2003), 37–92.
- Ghislain Baury. "Los ricoshombres y el rey en Castilla: El linaje Haro, 1076–1322." Territorio, Sociedad y Poder: Revista de Estudios Medievales, 6(2011), 53–72.
- José María Canal Sánchez-Pagín. "La Casa de Haro en León y Castilla durante el siglo XII: Nuevas conclusiones." Anuario de estudios medievales, 25(1995):1, 3–38, cf. esp. pp. 10–19 for Lope Díaz I.
- Ángel J. Martín Duque. "Vasconia en la Alta Edad Media: Somera aproximación histórica." Príncipe de Viana, 63(2002):227, 871–908.
- Gregorio Monreal Zia. "El Señorío de Vizcaya: origen, naturaleza jurídica, estructura institucional." Anuario de historia del derecho español, 43(1973), 113–206.
- Luis Salazar y Castro. Historia genealógica de la Casa de Haro. Madrid: Dalmiro de la Válgoma y Díaz-Varela, Madrid, 1959.