Oxford is not a campus you tour from a gate. The colleges sit inside a city that also has a river, a covered market, and people who are not visiting. The famous silhouettes — the Radcliffe Camera, the spires, Christ Church meadow — are real, and they are better early, before the pavement fills.
You can do the set pieces in a day from London. A night lets you walk them again after the coaches have gone, which is when the stone looks like it belongs to the place.
See
Radcliffe Square
The Camera, All Souls and St Mary’s. Stand in the square first. A college interior is optional, not the whole morning.
Christ Church meadow
Free, flat, and the best way to understand how the college sits on the river. The hall is a ticket.
The covered market
Lunch and a book, not a souvenir crawl. It is still a market.
A punt only if the queue is short
The Cherwell at Magdalen is the quieter water. The Thames at Folly Bridge is the busier one.