The status of the Eagle Owl in Britain has had a chequered history. In recent years several key investigations have been undertaken looking at the fossil record and evidence of contemporary records. These are summarised in a BOU paper in British Birds in 2008.
The Eagle Owl in Britain. Melling, T., Dudley, S. & Doherty, P. 2008. British Birds 101: 478-490. View.
Status and movements of Eagles Owls in Europe. Melling, T., Dudley, S. & Doherty, P. 2011. British Birds 104: 544-546. View.
Eagle Owl painting by Richard Allen