I will add that many of these aeroplanes, for whatever reason, cannot be considered failures. Some were of course, but many others were overtaken by events. I guess I should have provided the contents list, which is:
One Blackburn B.20 and B.40
Two Blackburn B.44
Three Blackburn B-48/Y.A.1 ‘Firecrest’
Four Boulton Paul P.92 and P.92/2
Five Bristol and Handley Page B.1/39 Bombers
Six Bristol Buckingham
Seven de Havilland DH.99/DH.101/DH.102 ‘Super Mosquito’
Eight Fairey Spearfish and Strike Fighter
Nine Folland Fo.108 and Fo.116
Ten Folland Fo.117
Eleven Gloster F.5/34
Twelve Gloster F.9/37
Thirteen Gloster E.28/39, E.5/42 and Rocket
Fourteen Handley Page HP.75 Manx
Fifteen Hawker Hotspur
Sixteen Hawker Tornado
Seventeen Hawker P.1005
Eighteen Hillson Bi-Mono and ‘Slip-Wing’ Projects
Nineteen Martin-Baker M.B.2
Twenty Martin-Baker M.B.3
Twenty-One Martin-Baker M.B.5
Twenty-Two Miles M.20
Twenty-Three Miles M.35, M.39 and M.39B Libellula
Twenty-Four Napier-Heston Racer
Twenty-Five Saunders-Roe A.37 ‘Shrimp’
Twenty-Six Short S.31
Twenty-Seven Short S.35 Shetland
Twenty-Eight Short S.36 and other Four-Engine Bombers
Twenty-Nine Short S.38 Sturgeon Torpedo Bomber
Thirty Supermarine B.12/36http://www.secretprojects.co.uk/forum/Themes/Aeroish/images/bbc/quote.gif
Thirty-One Supermarine 322 ‘Dumbo’
Thirty-Two Supermarine Spiteful and Seafang
Thirty-Three Vickers 432
Thirty-Four Vickers Windsor
Thirty-Five Westland Welkin
Appendix One One-Off Modifications to Production Aircraft:
A Photographic Gallery
Some tasty aircraft here. Some of course were never built but their qualification for inclusion comes from having serial numbers allocated. Others like the Gloster F.5/34 get in simply because they were still flying in September 1939.