Hi Trish,
I will gladly search the Kelshall PRs for a possible burial on my next visit to HALS. However, have you discounted the Samuel CHAPMAN age 51 born Herts shown in the 1871 census as visiting the home of George CHAPMAN, (age 30 also born Herts) at 10 Queens Place, Islington under ref. RG10/303 F.66 P.56.? Reference to IGI and previous census returns makes it a possibility.
Just a thought.
Regards ... Peter