Frist thanks to peter for bringing those short neck Emitron pictures. It seems that 3 are known to survive, including the prototype one.
This encouraged me to update that section of the cameramuseum,
http://www.tvcameramuseum.org/emi/em...36/1936p7a.htm
I have found the picture I took of the Emitron (long neck) tube in the bowels of Television Centre in the display cabinet. It's not a good picture, poor light, haste, etc. There is also a smaller Pye Photicon tube in the picture.
I would love to know what became of this collection of tubes. They did not from part of the public auction sell off.
Brian