Some years ago, one of the UK's air traffic control systems needed to be uplifted off the deprecated hardware it ran on. Going anywhere near the code itself was

Some years ago, one of the UK's air traffic control systems needed to be uplifted off the deprecated hardware it ran on. Going anywhere near the code itself was a total no-no - even though there were known glitches, the risk of touching that code was just deemed too high. So they instead wrote an emulator for the old machine and ran the unaltered s/w that way. Never underestimate the power of legacy that works.