A collection of wonderfully stretching test papers by Trifon Madas of University College London (UCL), with worked solutions. MyMathsCloud says these are the hardest papers out there – and that’s not reckoning with those that are explicitly marked ‘very hard’. I reckon they’re challenging but always rather fun to do.
These have been checked against the published mark schemes so they’re basically correct, but they don’t pretend to be polished final products.