In the early 1990s we met as postdocs in Cambridge just after finishing our PhDs in geophysics and geochemistry. We engaged in an informal discussion on lithospheric mantle melting in convergent orogens that was guided by two questions: (1) how can plutons have a mantle source signature in cold convergence zones; and (2) be located in the downgoing plate? The ‘slab breakoff’ hypothesis emerged. Here we review from our personal perspective how the idea was originally developed. We then provide our view looking back from our role as spectators, given that we have left the topic after the design of the hypothesis.
