Best I could find at this stage regarding the Cranford Agreement:
a. The Cranford Agreement (as it applies today)
29.This is a 1950s undertaking to avoid easterly take-offs from the northern runway (09L) over Cranford when ever possible. Until the main runways were extended westward in the 1960s Cranford was the nearest residential area to the airport situated under the approach and departure tracks. It is not a written agreement, but is understood to have been a "best endeavour" undertaking given at a public meeting in 1952. The main effect of the restriction is to require take-offs to use the southern runway (09R) during easterly operations, which in turn means that most easterly landings must overfly Windsor and Poyle to use the northern runway (09L), thereby precluding runway alternation during easterly operations in the daytime.
(DfT Website:
http://www.dft.gov.uk/stellent/group...503451-03.hcsp)