The slow maturation of true Orthodox life, in its fullness, without “one-sidedness,” is precisely that - slow maturation of true Orthodox life. St. Vladimir, Prince of the Rus, received Baptism in 988 A.D., but the story of Orthodox life in Russia generally marks the life and ministry of St. Sergius of Radonezh in the 14th century as the point at which there came a flowering of Orthodoxy in its fullness in that land.
This quote is from a longer blog post by Fr. Stephan Freeman. I excerpt it here becomes it seems to go well with the passage from Chesterton quoted earlier.
