Update; Is this Pitman Shorthand?
He was an aircraft engineer in the RAF based in Locking, Weston Super Mare, Somerset, UK. He volunteered for the RAF as he knew he was going to be conscripted in around 1938 - 1939.
Try posting this to r/translator , to see if anyone knows the origin of the symbols. Looks like some sort of handwritten Dravidian language to me, but is most likely shorthand.