Question:
Which position did Alfred Robens, Baron Robens of Woldingham hold in Apr, 1950?

Context:
 Alfred Robens, Baron Robens of Woldingham holds the position of Shadow Foreign Secretary from Dec, 1955 to Nov, 1956. 
 Alfred Robens, Baron Robens of Woldingham holds the position of Member of the House of Lords from Jun, 1961 to Jun, 1999. 
 Alfred Robens, Baron Robens of Woldingham holds the position of Member of the 40th Parliament of the United Kingdom from Oct, 1951 to May, 1955. 
 Alfred Robens, Baron Robens of Woldingham holds the position of Member of the 41st Parliament of the United Kingdom from May, 1955 to Sep, 1959. 
 Alfred Robens, Baron Robens of Woldingham holds the position of Member of the 38th Parliament of the United Kingdom from Jul, 1945 to Feb, 1950. 
 Alfred Robens, Baron Robens of Woldingham holds the position of Member of the 39th Parliament of the United Kingdom from Feb, 1950 to Oct, 1951. 
 Alfred Robens, Baron Robens of Woldingham holds the position of Member of the 42nd Parliament of the United Kingdom from Oct, 1959 to Oct, 1960. 
 Alfred Robens, Baron Robens of Woldingham holds the position of Representative of the Parliamentary Assembly of the Council of Europe from May, 1952 to Dec, 1954.

Answer:
Member of the 39th Parliament of the United Kingdom