Well, in the 1851 census there's Esther Allen, widow, needlewoman residing at Dyer Street, Christchurch, Southwark. Her recorded age is 119.
The only thing is ... her relation to the head of household was given as mother-in-law: so I think he was just having a laugh.
The same applies for Mary Benton at West Moor, Elton, Stockton. She is also said to be 119 years old. But she's the grandmother of the head of household Richard Almond, and he was only 22 years old. So I think HE was having a laugh, too.
In Pitlake, Croydon, there's ANOTHER 119 year old Eliza Dickson, widow and head of the household. But her daughter Eliza Dickson, a schoolmistress, is only 33. So I think again, the census form was completed by the literate daughter, who decided to have a laugh.
FindMyPast gives a fourth 119 year old too ... but that one is clearly a transcription error.
On the other hand ... Martha Dunsdale of Nelson Square, Southwark, born in Eaton Socon, Cambridgeshire does appear to have a legitimate claim to be the oldest person on the 1851 census. She is the only person in her household so must have completed the return herself (or given her answers to the enumerator in person) ... and she is 112 years old.
Of course, once you're that age your memory does tend to go a bit ...