Abstract Motivated by the theoretical work of Boyer [T.H. Boyer, J. Phys. A: Math. Gen. 39 (2006) 3455] plus the quite recent interferometric experiment of Shinohara, Aoki and Morinaga [K. Shinohara, T. Aoki, A. Morinaga, Phys. Rev. A 66 (2002) 042106] in which the scalar Aharonov–Bohm effect was studied, we re-open the extension to neutral particles carrying a magnetic moment and passing through a region of intense electric field, treated theoretically by Aharonov and Casher (AC) and independently by Anandan. An alternative interpretation of results on (a) neutrons and (b) T l F molecules to that afforded by AC is shown to involve only (i) the de Broglie wavelength of matter waves and (ii) the prediction from Maxwell's equations for the change in velocity of a neutral moving magnet as it enters or leaves an electric field. The exquisite sensitivity of experiment (b) allows a fractional change in velocity of order 10 −15 to be quantitatively determined.