As a university UCL> KCL> York. For your subject I think King's edges it slightly, simply because they have a fantastic alumni and faculty in the field and the research produced by King's is far better than UCL for history with many more citations. King's is also ranked higher than UCL on this year's QS World Rankings for History. It really boils down to what you want really. I know for a fact that KCL has a brilliant reputation internationally (in some countries including my own, even better than UCL). As a university currently, UCL is better with an overall world ranking of #7 whereas King's is #19. Do NOT follow UK based rankings such as Guardian and CompleteUniversityGuide because they rank universities on student satisfaction, putting Surrey and other universities ahead of even LSE, UCL, and King's. The fact is that Durham and Warwick, although amazing universities, won't be able to over take the brand name built up by UCL, LSE and KCL simply because the three have several Nobel Prize winners and others that have changed the course of the world. From a student that studies History at Oxford, we use a lot of KCL produced work for one of our war history modules.