I am trying to identify the name of a film I saw many years ago.
 The plot of the film goes something as follows:

- Man returns from World War 1 having lost memory of his life prior to the war
  as a result of wartime incident.
- Despite lost memory becomes successful business man
- Marries his 'secretary'
- discovers with help of current wife that he was a British (Parlamentary) MP 
  before the war.
- His former Secretary was in fact his wife before war.
   
  His former wife had recognised him but rather than immediately
revealing her identity felt it better to initially become his
secretary and she would then (over a period of time) help him to
recover his memory of his pre war career.

 The film was in Black and White and could have been made any time from 
 1930 to the early 1950's 

 It was almost certainly a British Film.
  
 Mongolia

Hello.

The movie is "Random Harvest" (1942).

"Amnesia, that standard movie plot device, was never used better than
in this filmed adaptation of James Hilton's popular 1940 novel. The
setting is England, where WWI veteran Colman is hospitalized for shell
shock, having lost his memory in battle...
...After much struggle, Garson locates her husband and gets a job as
his secretary (on a psychiatrist's advice, she doesn't let on who she
is). Colman has a new fiancee and is embarking on a political career.
But since he still fails to recognize his ex-wife..."
source:tvguide.com
http://www.tvguide.com/movies/database/showmovie.asp?MI=17541

Video from Amazon.com:
http://www.amazon.com/exec/obidos/ASIN/6301978536/

Book from Amazon.com:
http://www.amazon.com/exec/obidos/tg/detail/-/0786705930/
-----

search strategy:
"his memory " "old movie" "world war"
"random harvest" amnesia wife

I hope this helps.

Dear Jugglar 
 
 Thank you for an incredibly fast answer.
 This was indeed the film I saw.
 Having read the review my own memory of the film plot was not 
 quite that accurate either.  
 
 Very best regards
 
  Mongolia

Thank you for the tip.
-juggler