= College puffer jacket
E.g.: https://thecollegestore.co.uk/products/ladies-oxford-college-puffer-jacket?variant=40590030864549 Black with 5 rows, on left chest "colege name", logo, "Oxford", and right chest optional initials (or sometimes other identifiers/nicknames) to help distinguish from all the other people's identical clothes.
This has a whitelabel version: https://www.workweargiant.co.uk/product/result-urban-holkham-down-feel-jacket/[], the name appears to be "Holkham Down Feel Jacket".
Circa 2020, these are likely given out by each <Colleges of the University of Oxford>[college] for free, and are widely used.
If you look 20 and wear one of those, it's almost an ID, you can get anywhere that does not require a key card, porters won't look at you twice!
* https://www.oxfordstudent.com/2019/03/25/in-opposition-to-stash/ In opposition to stash by Morgan Jones (2019), basically because university is your last chance to wear what you want on many professions.