What follows is a long thread prompted by the (many) recent tweets about efficiency, impact, evidence etc. The thread summarises what I have learned in near 20 years. My current position is different from where I started. 1/n Impact was a dirty word in the early ‘00s. Many charities hated the subject being raised, especially by people they regarded as interlopers such as @npcthinks. That has changed a lot, but charities still don’t embrace and own the subject enough. 2/n