They also identified several young people who were with him at various points along the way.

So what we'd like to do, is identify people at that stage and hold them there.

"I think you identify good people and leave them alone," he said.

"They might also identify people who should be kept out," he added.

He is even able to identify people by scent alone.

When dogs are asked to identify people, the situation is even more complex.

About 1790 a key was published which identifies many people in the painting.

The researchers identified 167 people who had been attending for a year or more.

The challenge will be to identify 28,000 people who can do the job properly.

This census should have been the first one not to identify people by race.