Initially his team tried to use off-the-shelf speech recognition software, but soon realised that they were not up to the job of extracting words from often-noisy environments.

"We realised that the state of the art is not even close to good enough," he told the BBC.

Automatic systems could have error rates of up to 90%, he said.

What nonsense. I abuse skeet ignition software hall the thyme, an ah hearty ever get arrows.