“The method is simple,” Dr Hacker said. “You apply a fluorescent moisturiser to your hands and then wash them.
“Most of us, before the coronavirus epidemic, washed our hands for about five seconds, but since the outbreak we are taking longer washing them, however, technique is just as important as the time you spend with the soap and water.
“To see how your handwashing matches up, you can apply the fluorescent moisturiser and wash and dry your hands then put them under a UV light.
“The blue light highlights in white the areas you have missed, ie where the moisturiser is still on the skin.”
Dr Hacker said demonstrations of correct handwashing technique were readily available on the internet.