Dark deeds afoot

Although I'm still working on the story of John Marshal - A Place Beyond Courage, I am also looking towards the next project which I'm due to start writing byn March 07. As usual there's no title yet, but I do know it's going to be about Roger Bigod, William Marshal's eldest grandson and will cover much of the reign of Henry III.
I've started preliminary researching and while doing so came across a primary source account of the terrible incident of the death of Roger's uncle, Gilbert Marshal. Roger had five Marshal uncles and all of them died without issue. Foul play is known in the case of the second son, Richard, and highly suspected in Gilbert's. The other three are anyone's guess but I suspect they were helped off the mortal coil since none of them made old bones.
According to Matthew Paris, Gilbert was killed at a tourney near Hertford. He had a new Italian destrier which he was having trouble controlling - he didn't have the equestrian or military skills of his famous father. His first vocation had been as a clergyman and it had been rumoured that he was 'inexperienced and useless as a knight.' His fate was sealed when he attempted to rein the horse in and his bridle leathers snapped off right beside the bit chains. Paris suggests that they had been deliberately cut so that they would snap under pressure. With no means of controlling the horse, it was almost inevitable that he would fall. Unfortunately his foot was caught in the stirrup and he was dragged for some distance, sustaining cuts, bruises and traumatic internal injuries from which he died in agony later that same day. The damaged state of his internal organs was remarked upon when he was eviscerated prior to his body being borne to London for burial in the Temple Church.
Gilbert's effigy bears poignant testimony to his demise - and perhaps something more down the ages. Whereas most knights of this period have their feet couched upon a dog or a lion, Gilbert Marshal's feet reside upon a serpent that is twisted round, chewing at his foot. I am led to wonder if this is a hint from the family that he was murdered as well as being a testimony to the manner of his death. Gilbert had plenty of enemies but I wonder who it was who gave the order to take him down. It's going to be interesting finding out.