If cutting metal is the definition, the daddy of them all has to be the VC-7/V.1000, whose prototype was apparently nearly complete in the sheds at Wisley when the project was cancelled
The Comet 2 and Comet 3 had a LOT of metal cut, as I understand it, before their projects was terminated. I believe many of the fuselages were subcontracted to Shorts in Belfast, then shipped over to the Chester plant. Eventually they went for scrap.
We could also pick up the Soviet Buran space shuttle project, they built as many orbiters as the comparable US project did, 5 real orbiters and 8 full-scale engineering prototypes, but I understand they never did an actual mission, just one (unmanned) orbit by one of the ships.