Wild wrote that he “found two villages, Upper and Lower Hinksey, and between them there lay a great swamp, so that the villagers could not pass from one to the other without many miles of a round.”

What happened?

Here's the answer for you Brian! 

They are now called North & South Hinksey, located about 1 mile south of Oxford in Oxfordshire (prior to the changing of the boundaries they were in Berkshired). 

The two villages are now connected with the Southern By Pass road.

Matthew Arnold also referred to these two villages in his poem The Scholar Gypsey. 

Here's my 1821 map of Berkshire whose boundaries stayed pretty much as here for another 150 years. I'll have a closer look later on at the area Brian is speaking of and other maps I have. 

 http://www.flickr.com/photos/paulhilton/6608427307/

 The "he" above that Oscar Wilde was writing about was John Ruskin who had comandeered a group of Oxford students-to include Wilde- who built a road halfway across the swamp when it was abandonded, thus not completed, as Ruskin had left for Venice so Wilde and his fellow students, went back to their universities.

The ring road around the west of Oxford was built in 1962 to become what is now the A34 which had been built in 1922 and had gone through Oxford and was re-numbered A4144 when the ring road was completed.

Looking at old Ordnance Survey maps shows the A4141 running between these two villages; its location looks to be incorporated into the new 1962 A34 trunk road by-pass.

Many thanks for all your help.

Brian