No it isn't, and didn't I read in one of the books that Agnes Low heard giggling in the background when she telephoned Bourtree Cottage shortly after the murders? There was also the incident of the simulation of noises of a sexual nature between the two at Moreshead Mansions, not that I believe their relationship was ever a sexual one.
I suppose we can't ascertain one way or another.
DI Jones said he heard a chuckle from Jeremy. Although he did think it might have been a cough. Overhearing a private moment between jeremy Bamber and Julie mugford
However if Jeremy Bamber is gulity. I do believe he told Brett Collins