This might be where you read about it. "The Blitz on Britain" by Alfred Price.
There is a photo of a Hurricane with 2 bombs under the wings. The caption says:
"During 1940 and the early part of 1941, experiments were conducted in Britain in air-to-air bombing as a means of breaking up enemy formations. The Hurricane depicted was carrying two 250 pound antiaircraft bombs, each fitted with a photoelectric cell to detonate it as it passed another aircraft during its fall. The photoelectric cells proved unreliable for this purpose, however, and the antiaircraft bombs were never used operationally by the RAF."
https://books.google.com/books?id=UI...%20RAF&f=false