Colchester Corporation 25, SWC25K, Bristol RELL / ECW B53F, new May 1972, and 18, 1296F, AEC Regent V / Massey H33/28R body, new in May 1957.
18 was withdrawn in 1972, the year this photo was taken - maybe Colchester sent their oldest and newest to the rally.
25 was reported as preserved with British Bus, West Ewell as at January 2003.

Photo taken by Eric Thompson, July 1972, Suffolk Showground HCVC Rally