Gents,
The Duke of Buccleugh and The Earl of Malmsbury founded what became the Labrador in the
1830's. by
1932 the stud book was well established and had been for many years. See the current Buccleugh website
Buccleugh Labs history I've worked my own dogs for the previous Duke and he was a smashing chap and a great supporter of gun dogs and game shooting.
The Thames in it's upper reaches near Oxford has been called the Isis since Adam was a boy. The reserve boat in the University boat race is named "Isis" to this day. Isis was a god in the Egyptian pantheon associated with healing. So the Duke in Downton might have called his dog "Isis" for several reasons.
Eug