Elephant in room.
Many many projects have been delivered to time, cost and performance with effortless competence. Many earlier, for less and better than requested.
Ask why MoD/Government steadfastly refuses to learn from, or even acknowledge, these successes.
And ask why complex ones can succeed, while simple ones fail.
The last time the PAC had a serious look at this, in 1999, they chose six test cases. Five failed the time, cost and performance test; one passed. Not one recommendation from the latter's Post Project Evaluation Report was implemented. Ask why. (And who).