Jeremy's first plan was to burn the house down,which was no financial loss in itself as it was tenanted by the Bambers but owned by the Henry Smith Trust. However as greed was the main motive for the murders(as it had been when he burgled the jewellers shop in New Zealand and the Osea Road Caravan Park)he realized that in case of fire valuable antiques would be destoyed including a Meissen clock and other family heirlooms. The remark that Jeremy cared for farming in the slightest was a complete joke,the reality being that Nevill's will tied Jeremy to the farm until his death,and as Jeremy told Julie when she asked him why he didn't just walk away:"Because I have got too much to lose".
So we have a situation whereby Jeremy is looking for an occasion when all five family members would be under the same roof,and this occurred at the Christmas of 1984,though Jeremy copped out,possibly through the feelings of the general Christmas spirit which may have permeated even Jeremy's godless existence. It is probable that he came to regret this missed opportunity as the desire to do away with his family becomes stronger as his avarice is heightened due to his constant living beyond his means,trying to impress at every social function as often nonentities like Jeremy do,and he witnesses the failing health of Nevill,June retreating into her despairing shell,Sheila teetering on the brink of destruction,guilty of omission in her sons' upbringing, and the sombre drawings of the twins on the mahogany table in the lounge at White House farm give him the raison d'etre he needs to exculpate himself morally-that he will be doing them all a favour really as they are all disturbed and frail and their deaths would be a mercy.
Jeremy's one strong point at Gresham's was arithmetic,inherited from his biological father Major Leslie Marsham who had a job in the field,and he realized that with school fees for the boys and psychiatric care for Sheila and possibly June in the offing which would eat into his inheritance he would cut and run and with the opportunity in the first week in August presenting itself Jeremy ventured to execute his evil plan.
The £436,000 inheritance was a net figure after all death duties had been paid. Jeremy had also inherited a flat in a fashionable area of London as a direct result of the killings,and finally had the trappings of success which allowed him to leave farming behind, and move him up the social scale,affording him the kind of life to which he had always aspired,yet which inadvertently his parents had always thwarted.