London Underground’s experimental porthole tube train

It’s December 1949 and an experimental tube train has been introduced on the London Underground — that had huge windows and portholes.
Three-quarter view of modified 1938-tube stock ‘A’ driving motor car no 10306 (c) TfL from the London Transport Museum collection
This was a converted 1938-stock train, officially number 10306, and it was to test the public’s reaction to having windows that were not the usual rectangular windows that trains came with at the time