We think it was built in 1835. It appears to have once been two houses that were turned in to one, but this has been hard to confirm. The challenge is that it makes it hard to determine who lived in which house at what time.
The house is named, not numbered. We started suspecting something when we noticed the houses on the terrace are numbered 1, 2, this house, 5, 6, etc. the facade of the house also resembles houses 1 and 2 in every way, except it has one central front door where they have two. It does appear to be an old door however. Inside there's two staircases. One has been described to us as the servants staircase, but it's really little different in size or style to the other staircase. There appear to have been alterations over the years to box in some sections, but the woodwork that's still there is the same style.
The census hasn't helped here. It sometimes says the house name, other times number 3, and one time we found it described as "3-4" in 1911, suggesting if it was turned in to one house it happened before then.
We're wondering how to confirm this, for example would they have needed to submit building plans for the work in this era.