Critical friendship is a flexible form of support for school colleagues and one that is increasingly being applied to different contexts, including the New Relationship with Schools and School Improvement Partners. The ESRC/TLRP "Learning How to Learn" (LHTL) project was interested in, among other things, the scaling up of innovation, and incorporated light touch critical friendship in its design. This article explores the role of the critical friend in LHTL, the factors that helped or hindered, and concludes that light touch critical friendship is dependent upon three interrelated conditions: trust on the part of the school colleague, engagement and commitment by both parties, and the critical friend's knowledge of the school. School Improvement Partners have limited contact with schools through "a single conversation", and are described in government documentation as "critical friends". However, it is argued that this is an erroneous use of the term, likely to have negative consequences. (Contains 1 note.)