[5] At the age of 8 he moved to Toledo, where his maternal uncle served at the prestigious post of the Cathedral dean;[6] he looked after Matías when the latter attended Latinidad y Humanidades course at the local Instituto Provincial de Segunda Enseñanza (periodically also private colleges in Madrid),[7] until the young Barrio became Bachelor of Arts in 1859 (cum laude).

[12] He followed a number of other classes, getting certified as archivist and librarian from Escuela Especial de Diplomática;[13] he also studied theology in Madrid and Vitoria, though sources differ as to the grade he reached.

[14] Barrio completed also some courses abroad; at the Paris École des Hautes Études he studied sanscrit, perfected in Madrid in the late 1870s.

[19] The couple had 4 children, José,[20] Carlos, Jaime and Blanca;[21] the family moved across Spain, following the professional lot of Barrio and his subsequent academic assignments.

[42] In Palencia he is recorded as an author of a small booklet named Tradiciones pernianas, published in 1871; a late version of earlier Romantic books on folk culture,[43] it described Palencian customs and gathered together local tales.

[61] As a Carlist deputy he spoke in defense of the Church[62] and is noted for condoning atrocities committed by the Catholic missionaries in the Spanish Guinea Equatorial.

[63] In June 1898 as leader of Carlist minority he abstained from giving advice when the prime minister Sagasta consulted the parties on continuation or termination of the war with the United States,[64] though 3 months later he voiced against accepting the Washington Protocol and along few deputies signed a manifesto to the nation, denouncing the treaty.

[71] At this role, together with his position at the Orduña university, Barrio became the heart and soul of the judicial and cultural organisation in the insurgent Carlist state,[72] though the actual Minister of Justice was Romualdo de Viñaret.

As at that time the conservative and liberal press was widely speculating about another Carlist war approaching, the appointment of a “notorious legalist”[81] and “conciliator”[82] Barrio might have been interpreted as calming the waters, though actual intentions of the claimant remain rather unclear.

[83] Barrio did not manage to prevent isolated and probably spontaneous outbursts of Carlist insurgency, especially the 1900 Badalona uprising dubbed "La Octubrada".

[84] As unlike many Carlist personalities Barrio was spared the resulting governmental repressive action, his primary task turned out to be reconstruction of the party, suffering from closures of circulos, suspension of periodicals and exile of its leaders.

[85] The reopening of circulos produced their visible reformatting, with increased female presence and more focus on youth, including sport (especially football).

[86] The resumption of press activities produced a conflict with de Mella, already averse towards Barrio,[87] as the claimant ordered his Jefe Delegado to purge El Correo Español of the Mellista influence.

[89] In 1903 the claimant intended to relieve him of some duties by forming Junta Central[90] with Barrio as president, but the body seemed inept and was dissolved after half a year.

[92] Except Navarre, where thanks to Barrio's conciliatory strategy towards Integristas the Traditionalists gained almost a monopoly in political representation,[93] in other regions of Spain these efforts remained rather fruitless.