In the 1851 census (Cambridge Barracks, Portsmouth) the enumerator consistently puts birth town first, then county. So I would guess that "Ludlow" is a mistranscription of "Sussex".
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Its very possible there is a mistranscription, though hard to understand on the 2 written words Ludlow and Sussex. With pronunciation by a person in his own in dialect or slang from were the person grew up, then the enumerators own interpretation of understanding that dialect in his own slang, bearing in mind he would be educated and most folk would be in illiterate them days.
My G Granddad 2 - born
Ballsall in Warwickshire (Pronounced lSounds like pronounced
'Bore -Sale] in Warwickshire) then he moved to Bolsover in Derbyshire by 1861 census put down as born
'Bulsel in Warwickshire'