<Li> 1981--1985: John Jones (b . 1923--d . 1998) </Li> <Li> 1985--1988: Antony Duff (b . 1920--d . 2000) </Li> <Li> 1988--1992: Patrick Walker (b . 1932) </Li> <Li> 1992--1996: Stella Rimington (b . 1935) </Li>

What are the two main divisions of mi5