Butler and Alsop provide a clear and thorough explanation as to why our proposal (Simms and Ernstson 2019), that the Lairg Gravity Low might be a buried impact crater translocated from further east, is incompatible with what is known of the structure of northern Scotland, and I concede that in this particular scenario they are probably right. My original paper (Simms 2015) was based largely on field observations that, amongst other things, indicated that the Stac Fada Member impact ejecta preserved at outcrop had come from the east (despite claims to the contrary by others; Amor et al. 2008, 2019). When I subsequently became aware of the LGL I realised that its location and scale, and the similarity of its gravity signature to other buried impact craters, raised the possibility that it might represent the source of the SFM. Understandably, considering its context, previous authors had considered it a tectonic structure (Leslie et al. 2010) although acknowledging that this interpretation was not straightforward. The suggestion that it might be a buried impact crater was broadly consistent with my field observations of the impact deposit but it was only one, albeit interesting, possibility hence the question mark in the title of my paper.

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