Irish food safety chief, Prof Alan Reilly; The Peter Boddy Slaughterhouse, in Todmorden, West Yorkshire, which was raided by police and the FSA / Reuters

David McKittrick speaks to the Irish scientist whose team first discovered the scale of the horse meat problem

When Professor Alan Reilly and his team conducted the first tests on a beefburger to show that it was, in fact, almost 30 per cent horse meat, they were astounded. They thought they had made a mistake.

“I couldn’t believe it – that’s telling you straight,” the chief Irish food inspector tells The Independent. “I thought, ‘You can’t have horse meat in beefburgers’.”

His reaction was not to make the results known instantly but to order more tests: “We went to the ends of the world to make sure the science stood up. Because we knew the tsunami of horse manure that was going to come down the track at us from people criticising our methods.”

Professor Reilly, who is the chief executive of Ireland’s Food Safety Authority, added: “We were aware of the consequences for Ireland as a producer of safe and wholesome food; we were aware of the potential damage there.

“I mean, I’d be selling The Big Issue out on the street now if we’d got this one wrong.”

He recalled looking at the results and thinking, “There has to be something wrong here.” But there was no mistake: he had the earliest indication of what would erupt into the international horse meat scandal.

Professor Reilly’s job is, in part, to check the authenticity of foods. So in recent years he has examined samples of cod and chips, and discovered that occasionally the fish would be some cheaper species.

His team has looked at what was advertised as Irish honey, and found that some of it was actually Chinese. Some “wild Atlantic smoked salmon” turned out to have been farmed in Scotland.

“This is the bread and butter of a food control agency like us – it’s the PC Plod work,” said the professor, a UN adviser whose 30 years in food safety have included spells with the World Health Organisation and the UK scientific civil service.

“We may look at a thousand samples every year and 99 per cent of them come back negative. But in this case – the first time we looked at beef – the thousandth one was labelled as a beefburger but was actually 29 per cent equine DNA.”

The authority’s survey focused on processed meat products including burgers at the cheaper end of the market.

But he was adamant that there was no intelligence or whistle-blower who had revealed irregularities. “We weren’t acting on a tip-off,” he insisted. “Contrary to some speculation, we were just doing the type of work that you do to protect consumers against fraudulent activities.

“Our ongoing work is guided by a combination of scientific risk assessment and ordinary common sense. When there is a temptation to put cheaper ingredients into a food and then charge top prices for it, there’s an opportunity for industry to dupe consumers.”

He had confidence in the Irish laboratory which carried out the initial test, describing it as one of the best in Europe. But he commissioned more tests “because we couldn’t go out with a story like this and be wrong”.

When a second round of testing produced the same result, samples were then sent to a lab in Germany which confirmed the findings. To be utterly sure, the professor then had the chromosome examined.

“We are required to base all our decisions on sound science and this was the best science that we had available,” he said.

“It took us two months to ensure that the methods were robust, that the science was right.”