MP40 or Vigneron magazines in a Lanchester

[Lee Enfield]

...snip... that the Sten was designed to take the 9mm magazines already in series production in the UK. This MUST mean Lanchester magazines already in production at Dagenham and NOT MP40. It might well be that the Lanchester was designed to take MP40 magazines but...............

As you state, the Lanchester was a "Britishized" MP28/2 and Lanchester and Sten mags are straight copies of (50 & 32rd mind you) MP28/2 magazines.

This story (usage of MP38/40 magazines) is in line with the incorrect idea of 7.62x51 Nato and 7.62x39 M.43 (and 5.56/5.45) interchangeability which is repeated by far too many soldiers and other minimally cognizant firearms users.