Mitcham accounts for about two thirds of Mitcham & Morden and I guess it accounted for about the same proportion of the old Mitcham seat when it included Beddington & Wallington. Of course before 1945 it included Carshalton as well (therefore the whole of the present Carshalton & Wallington seat which would now constitute a majority of the electorate but may not have done before 1945 - certainly not in 1923!)
Any maps of these old boundaries around? I'm really curious now which seats the Merton bits around Streatham Vale, Tooting and Colliers Wood were in at different points in history.
I'm ruling out Streatham and/or Wandsworth Central as I don't think there were any LCC area seats that crossed into Surrey (at least not after 1900 or thereabouts).
I don't think Mitcham & Morden (and the predecessor Mitcham constituency) has had a voluntary retirement since WWII at least
Siobhan McDonagh (current MP) Angela Rumbold (unseated in 1997) Bruce Douglass-Mann (unseated in 1982 by election after defection) Robert Carr (Mitcham MP for absolutely yonks; stood in Carshalton instead of Mitcham & Morden after boundary changes in 1974)
The seat was only created in 1974 as around quarter of the present seat was in Merton and Morden which included Janet Fookes(only predecessor member still living) and Humphrey Atkins
2005 to now John Penrose (elected as a gain) 1997 to 2005 Brian Cotter (Elected as a gain and beat a new Conservative candidate then defeated) 1969 by-election to 1997 Jerry Wiggin (retired) 1958 by-election to 1969 David Webster (died) 1934 by-election to 1958 Ian Orr-Ewing (died) 1918 to 1923 and 1924 to 1934 by-election Lord Eskine (unseated, re-elected as a gain, went on to be Governor of Madras Presidency) 1923 to 1924 Frank Murell (elected as a gain then defeated and only the second non Conservative MP for Weston) 1918 to 1922 Sir Gilbert Willis (moved on to another seat)