Graham O
In general terms you are correct, but the project cited was very high risk, the focus of Public Accounts Committee scrutiny and weekly scrutiny by DEC (OR). This, because six previous attempts to get it up and running had failed and the last attempt was to be the final one - hence the close scrutiny and monitoring.
I don't know your background but you may understand the significance of a single tender, split prime programme, which has been re-endorsed? The last means you don't have your 20% tolerance. Having split primes means MoD has accepted they own a lot of risk as they sit between the two companies, with each dependent on MoD. Single tender is (wrongly in my opinion) a no-no but permission was granted at 4 Star level in this case due to previous failures and the expectation it would never get to contract anyway.
It was of particular embarrassment because our allies had complained we did not have a certain capability, making interoperability nigh on impossible. (Not that interoperability is policy, but you try to sneak it into the spec if possible).
"Embarrassment" is the key word. Turning such a programme round successfully made a lot of people twitch and, in the words of the 1 Star, "Set the bar too high" for other staffs. Perhaps that was why a number of attempts were made to cancel the programme. That they didn't succeed was largely due to Full Production being quietly launched before seeking approval to enter Development. (When detractors are trying to cancel your programmes for the wrong reasons you have to be creative). But, they get you in the end! But you got your capability.
Hope that explains a few things.