The diverse massive stellar population in the young massive clusterWesterlund 1 (Wd 1) provides an ideal laboratory to observe and constrain mass-loss processes throughout the transitional phase of massive star evolution. A set of high sensitivity radio observations of Wd 1 leads to the detection of 18 cluster members, a sample dominated by cool hypergiants, but with detections among hotter OB supergiants and WR stars. Here the diverse radio properties of the detected sample are briefly described. The mass-loss rates of the detected objects are surprisingly similar across the whole transitional phase of massive star evolution, at ~ 10<sup>-5</sup> M<sub>o</sub> yr<sup>−1</sup>. Such a rate is insufficient to strip away the H-rich mantle in a massive star lifetime, unless the stars go through a period of enhanced mass-loss. The radio luminous star W9 provides an example of such an object, with evidence for two eras of mass-loss with rates of ~ 10<sup>−4</sup> M<sub>o</sub> yr<sup>−1</sup>
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