Leo 251 was a patrikios and sakellarios; during a period of Arab attacks on Asia Minor, and after the capture of Amorion (in 838) Leo 251 visited St Ioannikios (Ioannikios 2) for his blessing; according to Petros 126 he was accompanied by Agapetos 4; during the visit he was approached by petitioners seeking the intervention of the empress Theodora 2 to secure the release of one of their relatives (Euandrios 1) whom the Arabs had captured; they discussed the matter with Ioannikios 2 who prayed and expressed his belief that the man would soon be freed; Leo 251 then left with Ioannikios 2's blessing: Petrus, Vita Ioannicii 62 (Λέοντα τὸν βασιλικὸν πατρίκιον καὶ σακελλάριον), cf. Sabas, Vita Ioannicii 50 (τὸν πατρίκιον καὶ σακελλάριον Λέοντα; a shorter version of the same story). The date is evidently after the fall of Amorion in 838. The reference to Theodora 2 suggests a date after the death of Theophilos 5, when she was regent for Michael III (Michael 11), but this is not conclusive as her influence may have been sought in such a matter when Theophilos 5 was still alive. Leo 251 was therefore in office some time between 838 and 846 (the death of Ioannikios 2).

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