In October 2015 the UK enacted legislation to permit the clinical use of two 
cutting edge germline-altering, IVF-based embryonic techniques: pronuclear 
transfer and maternal spindle transfer (PNT and MST). The aim is to use these 
techniques to prevent the maternal transmission of serious mitochondrial 
diseases. Major claims have been made about the quality of the debates that 
preceded this legislation and the significance of those debates for UK 
decision-making on other biotechnologies, as well as for other countries 
considering similar legislation. In this article we conduct a systematic 
analysis of those UK debates and suggest that claims about their quality are 
over-stated. We identify, and analyse in detail, ten areas where greater 
clarity, depth and nuance would have produced sharper understandings of the 
contributions, limitations and wider social impacts of these mitochondrial 
interventions. We explore the implications of these additional considerations 
for (i) the protection of all parties involved, should the techniques transfer 
to clinical applications; (ii) the legitimacy of focussing on short-term gains 
for individuals over public health considerations, and (iii) the maintenance and 
improvement of public trust in medical biotechnologies. We conclude that a more 
measured evaluation of the content and quality of the UK debates is important 
and timely: such a critique provides a clearer understanding of the possible, 
but specific, contributions of these interventions, both in the UK and 
elsewhere; also, these additional insights can now inform the emerging processes 
of implementation, regulation and practice of mitochondrial interventions.