For Anglo-Saxon, Norse, and Celtic, the personal statement should not read like a general love letter to the Middle Ages. Use 2 or 3 precise examples: a text, a historical problem, a language feature, a manuscript, a place-name, or an object that made you think differently.
The course has no required A Level subjects, but Cambridge recommends English language or literature, History, and ancient or modern languages. That means the statement has to show subject readiness through the way you handle evidence, not through a single compulsory school syllabus.
It is worth connecting your reading to the structure of ASNC. The first-year course is deliberately broad: students choose six subjects from a list of ten and are examined in four, before later specialisation. A good statement can show why that mix matters to you without repeating the whole paper list.