The Owl and the Pussy-cat went to sea [going offshore obviously]
Pussy said to the Owl, 'You elegant fowl!
The big clue is in that penultimate line. Leaving the UK for a year and a day is the minimum period of absence required to ensure that they secured non-resident status under the rules then in place.
The above analysis was offered by Andrew Hubbard, newly installed President of CIOT, after the Chartered Tax Advisers' address last night on the anniversary of Edward Lear's birthday.