22 The key to the prosecution case in summary was that Mr Presland built the keel fin (constructed separately to the hull), but not the bulb at the end that provided ballast weight, that the cutting of the keel and the welding occurred before the completion of the construction of the keel, including the attachment of tube (or pipe) at the leading edge of the keel and a 'box' on top (still seen on the keel stump produced at trial), and that, in these circumstances, only the applicant would have been responsible for the cut and welding back together of the separated pieces of keel skins. There was no evidence of anyone else working on the keel fins, except Mr Harris a boilermaker/welder who helped out. There was however no evidence that the accused was observed cutting the keel and welding it as alleged. It was agreed at trial that the horizontal cut occurred after the first cover plate for the ram compartment placed on one upper side of the keel had been made by Mr Presland, but before a second, or replacement, ram cover plate, apparently bigger than the first, was cut and had been welded into place. It did not matter, on one view, for the purposes of proof of guilt, as to what was the reason for the horizontal cut and welding. On the other hand, as the evidence suggested that the fitting of the hydraulic ram had nothing to do with the applicant, the Crown case was stronger if another reason could be established or pointed to in the evidence. There were three or four possibilities identified as reasons for cutting the keel in the view of Mr Gray, the prosecution's lead expert on metallurgy issues. These included, an inference that the cutting and the welding was to accommodate the aerofoil shape of the keel, to overcome shrinkage from welding the skins and gussets or ribs, to bend the sheets down to be welded together or, to enable the ram "compartment" to be expanded or adjusted to house the hydraulic ram to be fitted or inserted.