Jill Jones responds to the news that royals and celebrities have been warned to watch their words when out and about

Regarding your article ( Royals and celebrities warned to watch words as lip-reading videos go viral, 15 March ), the public needs to be aware that lip-reading is not an exact science and research shows that only about 30% of information can be seen on the lips in the best of circumstances. This is because the remainder of speech shapes are inside the mouth, hidden from view.

So lip-reading is very much guesswork and relies on a great deal of factors, including having good English competency, which many congenitally deaf people do not have due to lack of support in education; having the person being lip-read close enough to see clearly, their head still, with slow, clear lip patterns; nothing hiding the mouth like beards or hands; having an accent that is familiar to the person lip-reading; plenty of facial expressions and gestures, and so on.