Special thanks are due to Euan McKenzie who undertook the onerous task of proofreading at long distance on short notice and in record time to an appropriately low uncertainty.
Thermionic design cannot proceed in a vacuum, so the author is grateful for the perceptive insights and insults freely offered by Stuart Yaniger over the recent years.
An annual celebration of awe and wonder has been the European Triode Festival. This delightfully civilised bacchanalia has humbled the author with splendid works of art and engineering whilst at the same time reassuring him that he was not alone. Thank you, Christian, for first inviting me, and even more thanks to subsequent organisers for successfully maintaining the momentum.