The last thing a new party leader needs is a predecessor breathing down their neck.
Which is why Harriet Harman's trying very hard to keep her thoughts on Jeremy Corbyn to herself.
But you can hear just how concerned she is about whether Labour's new leader can really connect with the voters Labour failed to convince six months ago.
She says the first big electoral test will come next May, not just in the London Mayoral election, but also votes for the Scottish Parliament, Welsh Assembly and local councils in England.
That might be when Harriet Harman's vow of silence is tested.
Certainly Mr Corbyn's second outing at Prime Minister's Questions was a lot more combative than his first, even ordering David Cameron to come "back to reality".
He senses the cuts to tax credits could be very damaging for the Conservatives, a way to challenge the Tories' claim to be the true workers' party.
And he chose to use fewer "people's questions", leaving space to challenge Mr Cameron on his responses, advice he'd been getting from all sides...
You can hear a longer version of Harriet Harman's interview in the next edition of my podcast, which will be online soon.