if we only consider chart shows since radio 1 started in 1967, the roster runs as follows:-
1967-72 - Alan Freeman
1972-78 - Tom Browne
1978-79 - Simon Bates
1979-82 - Tony Blackburn
1982-84 - Tommy Vance
1984 (jan-sept) Simon Bates again
1984-86 - Richard Skinner
1986-90 - Bruno Brookes
1990-92 - Mark Goodier
1992-95 Bruno Brookes again
1995-2002 - Mark Goodier again
2003-05 - Wes Butters
2005-?? JK & Joel
the new chart did indeed used to be announced on a tuesday, during the lunchtime show - at 1 time Alan Freeman used to read out the rundown at 1pm.