Justinian I

"...On April 1, 527, Byzantine Emperor Justin I named his nephew Justinian I as co-ruler and successor to the throne. From the article:

The Codex Justinianus
Early on in his reign, Justinian commissioned a legal expert in his court, Tribonian, to gather together numerous legal notes, commentaries, and laws of the Roman legal system into a single text which would hold the force of law: this was the Codex Iustinianus. In 529 CE the first edition was published, followed in 534 CE by a revised second edition (which unlike the first, survives today). The text is divided into titles relating to specific aspects of the law, and was composed in Latin. It contained laws on heresy, orthodoxy and paganism as well.

Justinian's Life by Procopius
Justinian is unique among Roman emperors in that his life was recorded in two separate sources by the same author. Procopius of Caesarea, who was a legal secretary to General Belisarius, composed De Bellis ("On the Wars [of Justinian]") between 545 and 553 CE, which records the successes and some failures of the military campaign the emperor launched. He also composed De Aedificiis ("On the buildings [of Justinian]") between 550 and 557 CE, a work describing in great detail the many building projects the emperor undertook during his reign. Procopius also composed the Anecdota (translated as "Secret History", less often as "Unpublished Things") between 550 and 562 CE that claims to reveal the reality of life in the imperial court. It details the alleged sexual activities of the Empress Theodora, the weak determination of the emperor, and the power that women held in the imperial court. Considering the very negative tone of the text, it is unclear if Procopius intended the work to portray a satirical take on life at court or a truer account of imperial life than is portrayed in the De Bellis or De Aedificiis. What is almost certain is that the Anecdota reveals that Procopius had lost faith in the regime of Justinian, in contrast to the positive feelings expressed in his earlier works.

Justinian is credited as one of the greatest emperors in late Roman and Byzantine history. His achievements in the fields of art, architecture, legal reform, and conquest are remarkable by the standards of any leader in history. The works of Procopius have contributed greatly to this understanding as well as criticisms of his regime. His Christian faith was evident in all the spheres of his enterprise, marking a step in the transition of emperors from leaders in war and politics to leaders of faith and patronage as well."