When Dorothy Sayers uses also in her novel The Documents in the Case, this indicates that the material that is added is at least as important as that to which it is added. She uses moreover, as Blakemore (1987) has observed, to indicate that the material that is added provides further evidence for a recently stated conclusion. Too is the 'elsewhere' additive. Sayers uses it when the information that is added confirms or contradicts a previous utterance or assumption. She also uses it when the material concerned is of lesser or greater importance than that to which it is added.
Levinsohn, Stephen H.
"Also, too and moreover in a novel by Dorothy L. Sayers,"
Work Papers of the Summer Institute of Linguistics, University of North Dakota Session: Vol. 45, Article 1.
Available at: https://commons.und.edu/sil-work-papers/vol45/iss1/1