Even worse, it wasn't clear how a gain would be measured because the metrics the work would be measured against were not clear from the outset.
It's a pretty polite report but the conclusion is scathing. No real gain and no real way of measuring the gain -- or in government speak, the campaign lacked "a consistent focus on key performance metrics from an early stage."
The GBP100m "Get Ready for Brexit" campaign was launched two months before the UK was due to leave the EU on Oct. 31st last year. You couldn't help but notice it on television, billboards, print, digital and radio.
There was a suggestion that the Government knew there was no way it could get the votes in the House of Commons to leave on that date and that to the contrary, a rival motion to delay Brexit until after an election would be passed instead.
Nevertheless, the campaign ran until just a couple of days before the deadline, when it was clear that it could not be met. By then the NAO estimates that just under half the GBP100m had been spent.
This was a small saving on what was expected to have been spent at that stage, making it clear that there was a final push due in the last few days of the campaign that would have spent the remaining half of the budget had it not been cancelled.
The charts accompanying the report show a pretty bleak picture of no discernible uptake in people checking the official website for information. It was running at around 36% of the population before the campaign began and hovered roughly around that point after the campaign began.
There was a leap in the number of electronic devices that had accessed the official Brexit check information online. However, this was just the number of devices, not the number of people. The NAO points out that somebody checking two or three times on the same device would be counted two or three times.
So it's pretty clear that the campaign had little effect, and an increase in electronic devices checking out Brexit preparedness information probably came from people who had already accessed the information previously.
Perhaps the most astonishing finding is that the main outcome of the campaign was to convince the UK public there was no way the country was leaving by Oct. 31st.
Before the ads ran, around half thought it was achievable. Within a fortnight of Boris committing up to GBP100m, the proportion of the public who thought the country would leave the EU on the given date slumped from 53% to 36%.
It means Boris' cabinet spent GBP46m to have little effect on preparedness through a campaign that only convinced the public it was a stunt and that the country had no chance of actually leaving on Oct. 31st last year.
That's quite an achievement -- spending that amount of money on a campaign that has virtually no impact other than to convince people that the thing you're preparing them for isn't going to happen.
The one good thing is that at least the Cabinet Office pulled out of committing the remaining half of the budget once it was clearly impossible for the UK to leave with no deal agreed with the EU.