From ‘Fenland River – The Story of the Great Ouse and its Tributaries‘ by Rodney Tibbs, as related by W.E Doran, Chief Engineer of the Great Ouse River Board in the foreword:
After a very pleasant dinner some years ago in one of the Cambridge Colleges a certain Don turned to me and said “Why is the Ouse like a flea?”. I was unable to to think of any reasonable answer to this conundrun. “Ha!” he said, “because it goes into Beds. and Hunts. and ends up in the Wash!”
I’m planning to walk the Great Ouse, the UK’s 4th longest river, later in the year, I’ve hiked a third of it already (King’s Lynn to Ely), there are some fine opportunities along the way for a spot of wild camping.