According to Wikipedia - so let's not take it as gospel - there are 'a lot' of pubs in Oxford. This cache is hidden - with permission - close to one. There's no need to buy anything here and you're not required to interact with staff or enter the building or its gardens.
But which pub? Where? It's time to talk AANDs - formerly Geolympix Puzzle Tokens, now generically Aluminium Alpha-Numeric Discs. This cache was hidden with five different ones within two miles of the given co-ords. The given co-ords are for the River Isis, as the Thames is known as it passes through Oxford. It's unknown if Liz Taylor ever drank from it.
N51° 4
. 
W001° 1. 
N51° 4 Green . Blue Bronze Green W001° 1 Green . Forest (dark green) Purple Bronze
Good luck and happy hunting! To reach this cache you will need to pass through a gateway, but not pass a gate. The co-ords were vague at best so remember, no need to enter private/commercial areas.