Superhuman speed.
It was usual for a battle between Heroic Spirits to appear superhuman. Even taking that into account, however, Saber’s swiftness was extraordinary.
Speed due to his fundamental abilities as a Heroic Spirit.
Speed boosted through magecraft.
Speed that could only be attributed to some kind of “divine protection” associated with anecdotes of his exploits and bestowed on him by the Throne.
By combining all of them, he darted his way across the cluster of buildings that had become his battlefield with singular speed even for a Heroic Spirit, circling as he slowly but steadily closed distance.
The Lionheart’s advance, once begun, was like a gale scything across land and sea. The peerless speed of his march was so great that legend had it “only a general blessed with protection against wind had finally succeeded in halting it.”

Fate/Strange Fake: Volume 5, Chapter 15 ("Gold & Lions II")