Media playback is unsupported on your device Media caption This advertisement, obtained by the BBC under Freedom of Information, has never been previously broadcast.

For years the UK's health professionals have been preparing for a pandemic flu outbreak that they fear could lead to huge numbers of deaths and seriously disrupt the functioning of the nation.

Above is one of the government advertisements that we would have seen if it had happened by now. Never previously broadcast, it was obtained by the BBC through a freedom of information request.

The ad uses the metaphor of falling dominoes to convey the impression of a menace moving rapidly and almost inexorably across the globe, accompanied by an ominous voiceover.

The counter-measures it recommends, such as hand-washing, appear to present only an isolated obstacle to the perilous progress of the disease.

Anxiety

If it seems pessimistic, it illustrates the kind of scenario that has been deeply worrying the National Health Service and emergency planners in the past few years. It was produced in 2006.

It can be difficult to assess the impact of a publicity message outside its intended context, but it would certainly seem to fit an atmosphere of fear. It shows the extent of anxiety that has existed at times in the Department of Health - and perhaps still should.

This ad is one of several similar executions commissioned by the department, to be deployed in the event of a sufficiently serious situation.

The swine flu outbreak in 2009 was not considered grave enough for this treatment, prompting instead the less fearful 'Catch it, Bin it, Kill it' campaign.

'Severe event'

Initially the Department refused to supply the advert to the BBC, on the grounds that they were intended for future publication. But they changed their mind after we appealed, accepting that it is likely to be some time before circumstances arise which could lead to their being broadcast.

In disclosing this material, the department stressed: "The 'Dominoes' creative execution was developed before swine flu, to be broadcast in the event of a severe pandemic. While swine flu was mild, a severe event could still occur at any point, and the department continues to make provision for this in its communications planning.

"We periodically review creative material to ensure continued effectiveness and salience in the same way that we review pandemic preparedness plans as a whole."

So it's possible that we could be seeing a lot more of this symbolism at some point in the future.

From the freedom of information viewpoint, this indicates how the law can provide access to video or audio material held by public authorities as well as the written word.

Update, 08:43, 9 June: Many thanks to all the commenters so far, and I'd like to reply to some of the points made.

My view is that the nature and level of government preparations for possible emergencies such as pandemic flu is a highly important issue, which could indeed turn out to be absolutely crucial to the nation's welfare under certain circumstances. It is therefore a worthy topic for public debate, journalistic scrutiny, and freedom of information requests.

Some commenters clearly disagree with this perspective. They are fully entitled to hold that view of course, but I think it's good for the public to be better informed about the government's strategy and level of preparation, and to discuss it. Indeed, the debate about the ad itself in the comments strengthens my view that it is a matter worth discussing.

As the Department of Health state, they naturally keep emergency communications under review. Possibly the various comments on the ad on this blog - both from those who like it and those who don't - could even help the DH refine its ads for the future.

Some commenters imply that I'm saying it's shocking for the government to spend money on this kind of publicity material. In fact, as anyone who actually reads my post will see, I said nothing of the sort.

Some of you think the government is doing a good job of preparing for such an emergency, others disagree. That's entirely up to you, and I certainly haven't expressed an opinion myself. But what I have tried to do is focus more public attention on the topic and give you some more information to help you make up your own mind on the matter.