Bulldog Drummond by Herman Cyril McNeile
Also known as "Sapper"
Hugh "Bulldog" Drummond, wealthy former officer of the Loamshire Regiment, dashing and strong (but not particularly handsome), places an advertisement in The Times expressing his desire for an adventure -- which arrives in the form of a reply from a young woman concerned for her father. Blackmailers, communist conspiracy, and foreign paymasters of the arch-villain Carl Peterson are encountered and lead to more adventure than Drummond ever dreamed of! The is THE classic novel by McNeile, made into more movies and TV series than any other character, ever, though disguised in some.