Hertzsprung–Russell diagram of the VFTS stars analysed in this paper. The solid and dashed black lines are the non-rotating stellar evolutionary tracks and isochrones of Brott et al. (2011) and Köhler et al. (2015), respectively. The Humphreys–Davidson (HD) limit is shown by the dot-dashed line in the top-right}. Black symbols represent stars which cannot be reproduced by the stellar models (for reference, stars cooler than 9000 K and hence removed from our sample are also shown in black). In the legend, we provide the number of stars of each class that are in our final sample and those where not all observables can be reproduced by the stellar models simultaneously in parenthesis. Symbols in grey denote stars that fall off the MS part of the stellar tracks and are hence treated as Hertzsprung-gap stars (Sect. 2.1), but the symbols themselves keep their meaning. The luminosities of the four classical WR stars in our sample are indicated by the arrows on the left (they have surface temperatures of 80–90 kK).