1) British slang for a show-off 
[St Trinian`s] Henry Cuthbert Edwards aka Flash Harry is a fictional character from the St. Trinian`s series of films who first appears in the 1954 The Belles of St Trinian`s and who may also be a spiv. The term refers to `an ostentatious, loudly-dressed, and usually ill-mannered man`. Sir Malcolm Sargent was also (and earlier) nicknamed `F...
Flash Harry is British slang for a show-off.