The Mathematics Admissions Test (MAT) is the entrance exam for Mathematics and Computer Science degrees at Oxford University*. Practical information and past papers with solutions can be found at the official MAT website. I’ve made loads of videos about questions from the 2016 to 2018 papers here:
I sat a version of this paper when I was accepted to Oxford to study Maths and I have helped a lot of students prepare for this paper whilst teaching at top private schools in London. I wanted to make quality advice about this paper available more widely and so made video solutions to all of the 2018 paper and a lot of the 2016 and 2017 papers, going through the answers and giving general advice.
*the MAT is also used by Imperial College, London and the University of Warwick.