[3] The first bishop for whom there is any documentary evidence was Belisarius, who served during the reign (from 249 to 251) of the Emperor Decius and faced the persecution waged under this ruler.

The bishop was dismissed from his position, accused of having been a libellaticus, i.e., a Christian who had offered sacrifice to the Roman gods to avoid arrest.

It was a suffragan of the Archdiocese of Braga[3] The next bishop, Sabinus, led the Christian community through the persecution of the Emperor Valerian.

The bishop was able to travel to Rome, from which he brought back what is believed to be a relic of the True Cross, for which he founded the Monastery of Santo Toribio de Liébana, where it is still preserved.

[3] The diocese maintains its own school of formation for its clergy, the Seminary of the Immaculate Conception, which was founded on 1 November 1766, with the current structure being built in 1799.