The City of London Law Society (CLLS), whose members include some of the largest international law firms in the world, has updated its Guide on English law opinion letters in financial transactions. The aim of the Guide is to save time and costs spent in discussing which law firm should provide an opinion letter, what should it cover and who may rely on it. The Guide is widely consulted by practitioners and well respected. The unabridged version (including full footnotes) is available at www.citysolicitors.org.uk. This article sets out an abridged version.