We construct a non-separable Banach space every nonzero element of which is a bounded derivative that is not Riemann integrable. This in particular improves a result presented in , where the corresponding space was found to be separable.
"Searching for Structures Inside of the Family of Bounded Derivatives Which are not Riemann Integrable." Taiwanese J. Math. 22 (6) 1427 - 1433, December, 2018. https://doi.org/10.11650/tjm/180403