Several years into the implementation of Colombia’s 2016 peace agreement, the country is experiencing scores of complications in the application of post-conflict justice mechanisms and much else. No negotiation could have anticipated all, or even most, of these complications. Negotiation and implementation are iterative processes by their very nature. Yet, with the benefit of hindsight, there are some important lessons that are worth summarising – some of which could make a difference in the country’s future, or indeed that of others.