arem: oh dear! I've gone and hijacked a thread which reads EGLL "west Coast" Departures ... meanwhile over the snowy Steppes, one hundred and eighty degrees in the opposite direction ...!
OK, my 'brief and glorious period' at SVO was from 24th September 1970 to 23rd December 1970. During that time, the only 707 I dealt with was 'HU. The 'special config' I referred to was the rear several rows of economy class being occupied by panniers containing the meals for the Trans-Siberian leg. One look at the Aeroflot flight kitchens was enough to decide that!
The eastbound flight number in fact was BA860, the westbound one was BA861. In BOAC the rule was even numbers eastbound and northbound i.e. EvEN.