Of all the functions that a senior civil servant has to perform, giving evidence to Parliament's Public Accounts Committee is without doubt the one they dread the most.
And of all the government departments that are called to account for their failings, HM Revenue & Customs can be guaranteed to get the hardest and most consistent kicking.
From failing to tackle tax avoidance scams, to sweetheart deals with multinational firms, or the appalling performance of its telephone helpline since 2010, the agency has been under scrutiny like never before.
Whitehall rumour has it that "days" are spent at HMRC in the run-up to such hearings with senior officials "game planning" their best lines of defence against the onslaught.
Until recently their strategy has been a bit like that adopted by a bullied child - don't antagonise the committee too much for fear of worse consequences.
In public, the organisation's leadership has tried not to "take on" MPs, with officials merely restating their case in uncontroversial language. But the strategy seems to have changed. In its response to the PAC's report on its failings, HMRC accuses members of using "selective and misleading figures" and making "unjustified criticism" which is "undermining confidence" in the tax system.
HMRC is finally saying in public what its officials have been saying privately for a long time - that the PAC is often unfair, doesn’t listen to what they say and can be wrong on points of law.
There is some truth to that. But it is also true that HMRC has a long way to go before it can claim to be a model of efficiency and there are very valid reasons why it gets such a tough time from Margaret Hodge and Co.
Lin Homer, HMRC's chief executive, needs to not just defend her organisation but be more open about its very real shortcomings. If she did so we not only might get a better tax authority but officials might also get a more sympathetic hearing.
Video: Margaret Hodge - HMRC not chasing big firms
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