The tutorial system is just for teaching, not grading. It does keep students honest with themselves about their progress when they’re personally put on the spot once a week in front of one or two of their peers.
The biggest contrast for me between Oxbridge and another red brick was the Oxbridge tutors aren't shy of saying "You've not done the homework, go away and stop wasting my time", whereas the red brick approach was to pick you up and carry you over the finishing line (at least until the hour was up).