Henley secured the Home Counties League title for the second successive year on a dramatic final day.
Their win over Aston Rowant, coupled with Oxford's victory over Wewlyn meant that Henley pipped the Hertfordshire side to the Division One championship.
Henley vice-captain David Allaway told BBC Oxford: "It was very strange to win it in that way.
"We had to concentrate on our game but we were getting updates from Oxford.
"We went into the day four points behind and although it would have been nice to have our destiny in our own hands, it did turn out nicely in the end."
Henley finished the campaign on 297 points with Welwyn second on 281.