And on that very first test, we just had a set of DNAs plotted at random really.

NPR: Pioneering DNA Forensics

In order to check it was the measures that had made the difference, they were stopped for a month - and DNAs increased.

BBC: Simple measures 'cut NHS missed appointments'

Changing to posters stating how many patients had attended their appointments in the previous month, in combination with the other two measures, cut DNAs by 31%.

BBC: Simple measures 'cut NHS missed appointments'

Asking patients who booked over the phone to repeat back the time and date of their appointments cut DNAs by 3.5% compared with the previous month.

BBC: Simple measures 'cut NHS missed appointments'