There is plenty of research showing a significant earnings premium on average for graduates regardless of background. Probably the most comprehensive work is the paper by the IFS ‘How English domiciled graduate earnings vary with gender, institution attended, subject and socio-economic background’. The Sutton Trust has also done many excellent studies on different aspects of this question which is actually a lot more complex than it sounds.

Which is the best university? It’s a seductive question to ask, but that doesn’t mean there’s a sensible answer. League tables, aka rankings, is the nonsensical answer you’re likely to get.