Geographically, The British Isles are the main islands of Britain and Ireland and all of their off-shore islands. The longest river in the British Isles is therefore the River Shannon in Ireland and the second longest is the River Severn in Britain - which is fractionally longer than the River Thames.
The River Shannon in the Republic of Ireland, at 386 kilometers, is the longest river in the British Isles
There are many river islands in the British Isles but no two comprise them
the river seven
The Shannon.
London.
London in England
The Barn Owl.
river seven
The United Kingdom has the largest population of the two British Isles nations. (UK & Ireland)
The River Dee
Amazon and several tens of thousands of rivers
Probably not, but it is the fastest flowing river in Scotland.