Oh that is very sad! Poor Charles, the son, to have lost both mother and father by the age of 6 too.
Thank you Jon for your brilliant research skills and also for the pointer towards Woolwich Cemetery, I have family there so next time I go I'll pay my respects to John Henry too. Thank you ShaunJ for the articles, much appreciated as always.
ALAMO - you questioned whether his marriage to Florence in 1920 was his first marriage. There is a record of a John Clarke aged 25 marrying a Julia Elizabeth Walford aged 32 in Trichininopoly, India in 1903. I do wonder if it's him. It says he's a Private in the Lincoln Regiment so there's that army link (though I imagine a good portion of British people in India in that time had an army link).
Anyhow, thank you everyone for your help, I'm very grateful. I would not have got as much information on John Henry Clarke on my own.