Well, - that so called 'expert' was wrong!
I'm attaching the cause of death bit from my Uncle's Death Cert, (1930) and it clearly says 'suicide'. I believe that the 'on a sudden impulse' comment was to spare the family from the stigma of depression... (OK, it won't attach here for some reason).
Of course, attempting suicide was a crime, until (I think) as late as the 1960's, - and so not something that people would have wanted to talk about.
Pinkteedee, - so many Daniel Thomas's in Wales at that time! Do you have a definate Date and Place of Birth, & was he Married? Also, so you have him on any of the Censuses?
Romilly.