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We have previously analysed the spectra of 135 early B-type stars in the LMCand found several groups of stars that have chemical compositions that conflictwith the theory of rotational mixing. Here we extend this study to Galactic andSMC metallicities with the analysis of ~50 Galactic and ~100 SMC early B-typestars with rotational velocities up to ~300km/s. The surface nitrogenabundances are utilised as a probe of the mixing process.  In the SMC, we find a population of slowly rotating nitrogen-rich starsamongst the early B type core-hydrogen burning stars, similar to the LMC. Inthe Galactic sample we find no significant enrichment amongst the corehydrogen-burning stars, which appears to be in contrast with the expectationfrom both rotating single-star and close binary evolution models. However, onlya small number of the rapidly rotating stars have evolved enough to produce asignificant nitrogen enrichment, and these may be analogous to the non-enrichedrapid rotators previously found in the LMC sample. Finally, in each metallicityregime, a population of highly enriched supergiants is observed, which cannotbe the immediate descendants of core-hydrogen burning stars. Their abundancesare, however, compatible with them having gone through a previous redsupergiant phase. Together, these observations paint a complex picture of thenitrogen enrichment in massive main sequence and supergiant stellaratmospheres, where age and binarity cause crucial effects. Whether rotationalmixing is required to understand our results remains an open question at thistime, but could be answered by identifying the true binary fraction in thosegroups of stars that do not agree with single-star evolutionary models(abridged).

astronomy and astrophysics

The VLT-FLAMES survey of massive stars: constraints on stellar evolution  from the chemical compositions of rapidly rotating Galactic and Magellanic  Cloud B-type stars