As far as I understand it, New Labour almost entirely purged the civil service when they came to power. Loads of people were made redundant, and new people brought in who didn't fully understand the way things worked, nor the implications of certain policy positions.
They lost so much experience with that strategy done because they thought the civil service was "Tory" and would stand in their way that they then had to bring some people back as 'consultants' to get the work done.
But it enabled to do certain things, like expand PFI practice into the public sector, without the civil service shutting it down because it would ultimately cripple the state, which is exactly what it has done. It's notable that the people who had significant reservations about the GRA in the HOL were former politicians that had worked at a high level within government. They understood the need to think about the domino effect.