David Cameron's message to Labour was that the party had learnt nothing from the past.
Like a substitute teacher finding out a class had missed out on a core lesson, the Prime Minister suggested that he would solve the situation.
He would remind Labour of its previous pronouncements on the economy.
That would show the party the error of its ways, he implied.
At least it would, er, just as soon as he could lay his hands on it.
That, perhaps, is the lesson when you want to throw something in your opponent's face.
It helps to have that something close by.
Labour's shadow chancellor Ed Balls, to whom all this was directed, need not have fretted.
There followed a rather long and uncomfortable silence, after which the Commons chamber broke into pandemonium.
Mr Cameron, it appeared, was struggling to find what he was looking for in the rather large bundle of notes Prime Ministers use to help them deal with the onslaught of questions at PMQs.
The Conservative leader started to go red in the face.
This set Labour MPs off even more.
At one point the Glasgow Labour MP John Robertson was told to calm down by the Speaker John Bercow.
The scene started to look not unlike a very loud mime performance.
Labour MPs started holding up their order papers and offering them to the Prime Minister, as if to say 'here, maybe it's in here?"
One Labour frontbencher even stood up and looked over the despatch box and down on the floor as if desperately helping the Tory leader find what his missing piece of paper.
When he did finally quote Ed Balls words to him the shadow chancellor saw on the frontbench nodding furiously.
Lesson, it is fair to say, most definitely not learnt.
Why are you making commenting on The Herald only available to subscribers?
It should have been a safe space for informed debate, somewhere for readers to discuss issues around the biggest stories of the day, but all too often the below the line comments on most websites have become bogged down by off-topic discussions and abuse.
heraldscotland.com is tackling this problem by allowing only subscribers to comment.
We are doing this to improve the experience for our loyal readers and we believe it will reduce the ability of trolls and troublemakers, who occasionally find their way onto our site, to abuse our journalists and readers. We also hope it will help the comments section fulfil its promise as a part of Scotland's conversation with itself.
We are lucky at The Herald. We are read by an informed, educated readership who can add their knowledge and insights to our stories.
That is invaluable.
We are making the subscriber-only change to support our valued readers, who tell us they don't want the site cluttered up with irrelevant comments, untruths and abuse.
In the past, the journalist’s job was to collect and distribute information to the audience. Technology means that readers can shape a discussion. We look forward to hearing from you on heraldscotland.com
Comments & Moderation
Readers’ comments: You are personally liable for the content of any comments you upload to this website, so please act responsibly. We do not pre-moderate or monitor readers’ comments appearing on our websites, but we do post-moderate in response to complaints we receive or otherwise when a potential problem comes to our attention. You can make a complaint by using the ‘report this post’ link . We may then apply our discretion under the user terms to amend or delete comments.
Post moderation is undertaken full-time 9am-6pm on weekdays, and on a part-time basis outwith those hours.
Read the rules hereComments are closed on this article