Herzen wrote about his uncle in the book My Past and Thoughts that "he received a decent education ... was very well–read ... served at some mission (as an advisor to one of the embassies), and when he returned to Saint Petersburg, he was made Chief Prosecutor".

The young, full of reformist plans, Emperor Alexander I needed an energetic person in the church department, which also expected changes.

Like the Chief Prosecutor Khovansky, he took up the problem of the annual balance of church money, which was a huge amount at that time – about 100 thousand rubles.

"Yakovlev is not quite good...", he said to Prince Golitsyn, "the clergy are completely dissatisfied with them; complaints against him are incessant, and it seems to me that he is incapable of being in the place of the synodal Chief Prosecutor".

In the future, the line of Yakovlev prevailed, who clearly outlined: the church reform, begun by Peter I, had not yet been completed, and there was still little justice and legality in the Synod.

The state was faced with two options: to introduce the laity into the synodal presence, as was established by Peter I, or to strengthen the institution of the Ober–Prosecutor's Office.

He was buried at the cemetery of the Alexander Nevsky Lavra (Necropolis of Artists) next to his wife, Olympias Zotova (1775–1865), the daughter of a Chief Officer and one of his many mistresses.